kernel message - HDD I/O error. and a java error

Hey
I had this problem earlier

I have a macbook pro late 2008 model running all the latest updates with snow leopard.
Over the past few weeks I have been having moments where my laptop will briefly freeze for up to a minute with the little loading cursor going, but nothing happening. It doesn't happen at a particular time, and not necessarily when there is a high workload.
On top of this, today when a java based game on the internet was being played, the screen started changing and flickering and the computer had to be shut off by holding down the power button.


Here are the error logs from examples of each incident


This is the freeze which caused me to shut down while playing the java game online...


11/07/10 5:32:18 PM kernel 45585f4d5f4857575f455352
11/07/10 5:32:18 PM kernel NVRM-RC: 1 3a30783830303030303033
11/07/10 5:32:18 PM kernel NVRM-RC: 0 4e565f5047524150485f5052495f545043305f5445585f4d5f4857575f455352
11/07/10 5:32:18 PM kernel NVRM-RC: 1 5f5245513a30783230303837613035
11/07/10 5:32:18 PM kernel NVRM-RC: 0 4e565f5046425f4d4d555f4c494d4954565f545241502830293a3078623230
11/07/10 5:32:18 PM kernel NVRM-RC: 0 4e565f5046425f4d4d555f4c494d4954565f545241502863686964293a307833
11/07/10 5:32:18 PM kernel NVRM-RC: 0 4e565f5046425f4d4d555f4c494d4954565f545241502832293a307830
11/07/10 5:32:18 PM kernel NVRM-RC: 0 4e565f5046425f4d4d555f4c494d4954565f545241502833293a307831663030
11/07/10 5:32:18 PM kernel NVRM-RC: 0 4e565f5046425f4d4d555f4c494d4954565f545241502834293a307832613162
11/07/10 5:32:18 PM kernel NVRM-RC: 0 4e565f5046425f4d4d555f4c494d4954565f545241502835293a3078300a
11/07/10 5:32:18 PM kernel NVRM-RC: 0 4e565f5047524150485f5052495f545043305f5445585f4d5f4857575f455352
11/07/10 5:32:18 PM kernel NVRM-RC: 1 5f414444523a30783261316230300a
11/07/10 5:32:18 PM kernel NVRM-RC: 0 4e565f5047524150485f5052495f545043305f5445585f4d5f4857575f455352
11/07/10 5:32:18 PM kernel NVRM-RC: 1 5f435458444d413a307834303030303436340a
11/07/10 5:32:18 PM kernel NVRM-RC: 0 4e565f5047524150485f5052495f545043305f5445585f4d5f4857575f455352
11/07/10 5:32:18 PM kernel NVRM-RC: 1 5f4d4d553a307831613166303030300a
11/07/10 5:32:18 PM kernel NVRM-RC: 0 4e565f5047524150485f5052495f545043305f5445585f4d5f4857575f455352
11/07/10 5:32:18 PM kernel NVRM-RC: 1 5f5245513a307832303038376130350a
11/07/10 5:32:18 PM kernel NVRM-RC: 0 4e565f5047524150485f5052495f545043305f50524f505f4857575f4553523a
11/07/10 5:32:18 PM kernel NVRM-RC: 1 30783830303030303430
11/07/10 5:32:18 PM kernel NVRM-RC: 0 4e565f5047524150485f5052495f545043305f50524f505f4857575f4553525f
11/07/10 5:32:18 PM kernel NVRM-RC: 1 434f4f52443a307830
11/07/10 5:32:18 PM kernel NVRM-RC: 0 4e565f5047524150485f5052495f545043305f50524f505f4857575f4553525f
11/07/10 5:32:18 PM kernel NVRM-RC: 1 464f524d41543a307831383030
11/07/10 5:32:18 PM kernel NVRM-RC: 0 4e565f5047524150485f5052495f545043305f50524f505f4857575f4553525f
11/07/10 5:32:18 PM kernel NVRM-RC: 1 53544154453a307833303030300a
11/07/10 5:32:18 PM kernel NVDA(OpenGL): Channel exception! exception type = 0xd = GR: SW Notify Error
11/07/10 5:32:18 PM kernel 0000006e
11/07/10 5:32:18 PM kernel 00200000 00008397 00000474 00000140
11/07/10 5:32:18 PM kernel 0000047e 00000dfc 00000000 00000003
11/07/10 5:32:18 PM kernel 00000000 00000000 00000013
11/07/10 5:32:18 PM kernel 00000140 00000000
11/07/10 5:33:10 PM kernel npvhash=4095


This is all that came up in the log for the most recent random freeze which lasts 30 seconds to a minute

11/07/10 5:41:03 PM kernel disk0s2: I/O error.
11/07/10 5:41:03 PM kernel