I was having the same problem. Even though I don't use typically use Safari, I didn't want to disable the multi-process windows (via the Debug menu enabled by "defaults write com.apple.Safari IncludeInternalDebugMenu 1").
I don't usually use Safari, but was using it to log into Facebook with a different account than my personal one, so I could test games. It turns out that playing a game on Facebook was a very reliable way to quickly reproduce this reloading-all-tabs behavior, and it didn't matter if it was a Flash game or html game. If I opened a new single-process window and played the game, it'd crash. It seemed to crash even faster if it was an html game.
So I tried all the suggestions that everyone gave in various threads here:
>> tried deleting ~/Library/Caches/com.apple.Safari/Cache.db -- didn't fix it
>> tried deleting ~/Library/Preferences/com.apple.Safari.plist -- didn't fix it
>> tried disabling Java -- didn't fix
>> tried emptying the cache (via menu) -- didn't fix
>> tried increasing to 500MB database storage -- didn't fix
>> tried deleting cookies and removing all site data (via prefs/privacy) multiple times -- didn't fix
>> tried uninstalling all extensions and disabling extensions -- didn't fix
Finally, I reset Safari.
Seems to have fixed it for me.
The only way I was finally able to resolve all tabs opening in Safari, was to first export all bookmarks for a backup, clear all caches, then delete all bookmarks, clearing all caches, close Safari, then import bookmarks.
Sometimes even importing back the Safari bookmarks did not work, so I exported my Google Chrome bookmarks and repeated the above process but this time importing the Chrome bookmarks. I did this about a month ago and have not had the problem recur with any Safari bookmarks, tabs, etc. I imagine if you have another browser's bookmarks (FireFox, et al) that you could use those exported bookmarks to import into Safari.
Hope this helps.
Completely resetting Safari (and losing all bookmarks and whatnot) did not help.
When I run an html game in a single-process window and it crashes, then the report consistently shows Thread 0 crashed and the stack trace indicates it happened when playing audio. It always shows the audio stuff in the stack trace. So I'm assuming that the problem is an audio bug, and that there's nothing I can do about it until Apple fixes it.
I'm running Safari 5.1.2 (6534.52.7) on a MacBook (aluminum MacBook5,1) still on Snow Leopard, w/8GB ram.
Thread 0 Crashed: Dispatch queue: com.apple.main-thread
0 libSystem.B.dylib 0x00007fffffe007c5 __memcpy + 37
1 ...pple.audio.units.Components 0x000000010fb2ac00 AUNetSendEntry + 35487
2 ...pple.audio.units.Components 0x000000010faa87d1 0x10faa4000 + 18385
3 ...pple.audio.units.Components 0x000000010facfe94 SystemOutputAUEntry + 1539
4 ...pple.audio.units.Components 0x000000010fb2c4df AUMultiChannelMixerEntry + 4785
5 ...apple.audio.units.AudioUnit 0x00007fff86869c6e AudioUnitSetProperty + 55
6 ....audio.toolbox.AudioToolbox 0x00007fff86e4156b SubmixGraph::ConnectInputChannel(bool, MixerChannel*, bool) + 425
7 ....audio.toolbox.AudioToolbox 0x00007fff86e42e07 AQMEDevice::AddRunningClient(AQIONodeClient*, bool) + 233
8 ....audio.toolbox.AudioToolbox 0x00007fff86e2600c AudioQueueObject::StartRunning(AQIONode*) + 60
9 ....audio.toolbox.AudioToolbox 0x00007fff86e215ca AudioQueueObject::_Start(XAudioTimeStamp const&, bool) + 638
10 ....audio.toolbox.AudioToolbox 0x00007fff86e2174f AudioQueueObject::Start(XAudioTimeStamp const&, bool) + 27
11 ....audio.toolbox.AudioToolbox 0x00007fff86e3a509 AQServer_Start + 54
12 ....audio.toolbox.AudioToolbox 0x00007fff86e3b843 AudioQueueStart + 169
13 com.apple.MediaToolbox 0x00007fff8301a031 FigAudioQueueStart + 554
14 com.apple.MediaToolbox 0x00007fff830603f0 figAudioQueueRenderPipelineSetRate + 602
15 com.apple.MediaToolbox 0x00007fff83058400 bossSetPossiblyOutsourcedTimebaseRate + 190
16 com.apple.MediaToolbox 0x00007fff8305e822 bossStartTimebaseAndAudioContext + 61
17 com.apple.MediaToolbox 0x00007fff8305f31f figPlaybackBossPrerollCompleted + 444
18 com.apple.MediaToolbox 0x00007fff8305f574 figPlaybackBoss_AllMentorsPrerollComplete + 31
19 com.apple.CoreMedia 0x00007fff84780461 figDeferredNotificationRun + 52
20 com.apple.CoreFoundation 0x00007fff85cd6bb8 __CFRunLoopRun + 6488
21 com.apple.CoreFoundation 0x00007fff85cd4d8f CFRunLoopRunSpecific + 575
22 com.apple.HIToolbox 0x00007fff8a3a57ee RunCurrentEventLoopInMode + 333
23 com.apple.HIToolbox 0x00007fff8a3a55f3 ReceiveNextEventCommon + 310
24 com.apple.HIToolbox 0x00007fff8a3a54ac BlockUntilNextEventMatchingListInMode + 59
25 com.apple.AppKit 0x00007fff8711deb2 _DPSNextEvent + 708
26 com.apple.AppKit 0x00007fff8711d801 -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] + 155
27 com.apple.Safari.framework 0x00007fff8103e2be -[BrowserApplication nextEventMatchingMask:untilDate:inMode:dequeue:] + 177
28 com.apple.AppKit 0x00007fff870e368f -[NSApplication run] + 395
29 com.apple.AppKit 0x00007fff870dc3b0 NSApplicationMain + 364
30 com.apple.Safari.framework 0x00007fff811fc924 SafariMain + 200
31 com.apple.Safari 0x0000000100000f1c 0x100000000 + 3868
I had just switched to Chrome a few days ago because I had it with this problem, saw the Safari update notification yesterday and got excited. Jumped back into Safari and within seconds saw that the problem was still there. I'm very disappointed at Apple on this one. I prefer Safari, but I am so sick of losing my work with this page refresh thing. Ugh.