Kernel Panic

Since the last update (2 or 3 days ago) my Mini has been hard-crashing (kernel panic, forcing me to shut down) at least once a day. I haven't had a hard-crash like this in probably a year or more. The last update included iTunes 10.2.1, Safari 5.0.4, and Java for Mac 10.6 Update 4.

Any ideas what may be causing this?
===================================

Interval Since Last Panic Report: 4483158 sec
Panics Since Last Report: 2
Anonymous UUID: 830348B5-8E64-485B-9B8D-97DAE50143C9

Fri Mar 11 08:22:06 2011
panic(cpu 1 caller 0x226b53): "thread_invoke: preemption_level -1, possible cause: unlocking an unlocked mutex or spinlock"@/SourceCache/xnu/xnu-1504.9.26/osfmk/kern/sched_prim.c:1471
Backtrace (CPU 1), Frame : Return Address (4 potential args on stack)
0x5724be18 : 0x21b50c (0x5d4438 0x5724be4c 0x223974 0x0)
0x5724be68 : 0x226b53 (0x58babc 0xffffffff 0x58ba54 0x226423)
0x5724bee8 : 0x227259 (0x74297c4 0x0 0x42bb3000 0x1)
0x5724bf58 : 0x2272c4 (0x22fc20 0x863ea0 0x0 0x2a358d)
0x5724bf78 : 0x22fdba (0x22fc20 0x863ea0 0x0 0x0)
0x5724bfc8 : 0x2a06cc (0x863ea0 0x0 0x10 0x7970404)

BSD process name corresponding to current thread: kernel_task

Mac OS version:
10J567

Kernel version:
Darwin Kernel Version 10.6.0: Wed Nov 10 18:13:17 PST 2010; root:xnu-1504.9.26~3/RELEASE_I386
System model name: Macmini3,1 (Mac-F22C86C8)

System uptime in nanoseconds: 77888165553093
unloaded kexts:
(none)
loaded kexts:
com.parallels.kext.prl_vnic 6.0 11994.637263
com.parallels.kext.prl_netbridge 6.0 11994.637263
com.parallels.kext.prl usbconnect 6.0 11994.637263
com.parallels.kext.prl hidhook 6.0 11994.637263
com.eltima.ElmediaPlayer.kext 1.0
com.parallels.kext.prl_hypervisor 6.0 11994.637263
com.microsoft.driver.MicrosoftKeyboardUSB 8.0
com.microsoft.driver.MicrosoftKeyboard 8.0
com.apple.filesystems.afpfs 9.7 - last loaded 3644688181923
com.apple.nke.asp_tcp 5.0
com.apple.driver.AppleHWSensor 1.9.3d0
com.apple.filesystems.autofs 2.1.0
com.apple.driver.ApplePlatformEnabler 2.0.2d1
com.apple.driver.AppleTyMCEDriver 1.0.2d2
com.apple.driver.AGPM 100.12.19
com.apple.driver.InternalModemSupport 2.6.2
com.apple.driver.AppleIntelYonahProfile 14
com.apple.driver.AppleUpstreamUserClient 3.4.5
com.apple.driver.AppleIntelPenrynProfile 17
com.apple.Dont Steal_Mac_OSX 7.0.0
com.apple.driver.AppleHDA 1.9.9f12
com.apple.driver.AppleMCCSControl 1.0.17
com.apple.driver.AppleIntelNehalemProfile 11
com.apple.driver.AudioAUUC 1.13
com.apple.driver.AudioIPCDriver 1.1.6
com.apple.nvenet 2.0.15
com.apple.driver.AirPortBrcm43xx 423.91.27
com.apple.driver.AppleIntelMeromProfile 19
com.apple.GeForce 6.2.6
com.apple.driver.AirPortBrcm43224 426.36.1
com.apple.driver.ACPI SMCPlatformPlugin 4.5.0d5
com.apple.driver.AppleLPC 1.4.12
com.apple.driver.AppleIRController 303.8
com.apple.iokit.SCSITaskUserClient 2.6.5
com.apple.driver.PioneerSuperDrive 2.5.8
com.apple.iokit.IOAHCIBlockStorage 1.6.3
com.apple.BootCache 31
com.apple.AppleFSCompression.AppleFSCompressionTypeZlib 1.0.0d1
com.apple.driver.AppleEFINVRAM 1.4.0
com.apple.driver.AppleAHCIPort 2.1.5
com.apple.driver.AppleUSBHub 4.1.7
com.apple.driver.AppleFWOHCI 4.7.1
com.apple.driver.AppleUSBEHCI 4.1.7
com.apple.driver.AppleUSBOHCI 4.1.5
com.apple.driver.AppleRTC 1.3.1
com.apple.driver.AppleHPET 1.5
com.apple.driver.AppleACPIButtons 1.3.5
com.apple.driver.AppleSMBIOS 1.6
com.apple.driver.AppleACPIEC 1.3.5
com.apple.driver.AppleAPIC 1.4
com.apple.driver.AppleIntelCPUPowerManagementClient 105.13.0
com.apple.security.sandbox 1
com.apple.security.quarantine 0
com.apple.nke.applicationfirewall 2.1.11
com.apple.driver.AppleIntelCPUPowerManagement 105.13.0
com.apple.driver.AppleHDAPlatformDriver 1.9.9f12
com.apple.driver.AppleProfileReadCounterAction 17
com.apple.driver.AppleProfileTimestampAction 10
com.apple.driver.AppleProfileThreadInfoAction 14
com.apple.driver.AppleProfileRegisterStateAction 10
com.apple.driver.AppleProfileKEventAction 10
com.apple.driver.AppleProfileCallstackAction 20
com.apple.iokit.IOSurface 74.2
com.apple.iokit.IOBluetoothSerialManager 2.3.8f7
com.apple.iokit.IOSerialFamily 10.0.3
com.apple.driver.AppleHDAHardwareConfigDriver 1.9.9f12
com.apple.driver.DspFuncLib 1.9.9f12
com.apple.driver.AppleHDAController 1.9.9f12
com.apple.iokit.IOHDAFamily 1.9.9f12
com.apple.nvidia.nv50hal 6.2.6
com.apple.iokit.IOFireWireIP 2.0.3
com.apple.iokit.AppleProfileFamily 41
com.apple.NVDAResman 6.2.6
com.apple.iokit.IONDRVSupport 2.2
com.apple.iokit.IOGraphicsFamily 2.2
com.apple.iokit.IO80211Family 312
com.apple.iokit.IONetworkingFamily 1.9
com.apple.driver.NVSMU 2.2.7
com.apple.driver.AppleSMC 3.1.0d3
com.apple.driver.IOPlatformPluginFamily 4.5.0d5
com.apple.driver.AppleSMBusPCI 1.0.8d0
com.apple.driver.AppleUSBAudio 2.7.6f4
com.apple.iokit.IOAudioFamily 1.8.0fc1
com.apple.kext.OSvKernDSPLib 1.3
com.apple.driver.BroadcomUSBBluetoothHCIController 2.3.8f7
com.apple.driver.AppleUSBBluetoothHCIController 2.3.8f7
com.apple.iokit.IOBluetoothFamily 2.3.8f7
com.apple.iokit.IOUSBHIDDriver 4.1.5
com.apple.iokit.IOSCSIBlockCommandsDevice 2.6.5
com.apple.iokit.IOUSBMassStorageClass 2.6.5
com.apple.driver.AppleUSBComposite 3.9.0
com.apple.iokit.IOSCSIMultimediaCommandsDevice 2.6.5
com.apple.iokit.IOBDStorageFamily 1.6
com.apple.iokit.IODVDStorageFamily 1.6
com.apple.iokit.IOCDStorageFamily 1.6
com.apple.driver.XsanFilter 402.1
com.apple.iokit.IOAHCISerialATAPI 1.2.5
com.apple.iokit.IOSCSIArchitectureModelFamily 2.6.5
com.apple.driver.AppleFileSystemDriver 2.0
com.apple.iokit.IOAHCIFamily 2.0.4
com.apple.iokit.IOUSBUserClient 4.1.5
com.apple.iokit.IOFireWireFamily 4.2.6
com.apple.iokit.IOUSBFamily 4.1.7
com.apple.driver.AppleEFIRuntime 1.4.0
com.apple.iokit.IOHIDFamily 1.6.5
com.apple.iokit.IOSMBusFamily 1.1
com.apple.security.TMSafetyNet 6
com.apple.kext.AppleMatch 1.0.0d1
com.apple.driver.DiskImages 289
com.apple.iokit.IOStorageFamily 1.6.2
com.apple.driver.AppleACPIPlatform 1.3.5
com.apple.iokit.IOPCIFamily 2.6
com.apple.iokit.IOACPIFamily 1.3.0