Non-Apple browsers cause cascading system hang with clean install of Lion

Question

It started with Google Chrome.  After a few hours of use, Chrome would randomly lock up one renderer at a time until it was completely unresponsive.  Console showed nothing conclusive in the logs, and would soon lock up itself.  Logged-in Terminal windows could sometimes get as far as a "ps auxc", but would lock up during the command output, and new Terminal windows or tabs would never get past login.  The SSH daemon would be dead in the water, preventing me from logging in remotely.  Any existing SSH connections would hang on the first command.  Activity Monitor would lock up the moment I tried to sample a process or interact with anything.  Interacting with SystemUIServer (pulling down the menu for the clock or trying to do a Spotlight search) would cause SystemUIServer to hang.  Same with the Dock.  My mouse was like the Midas of software failure: everything I touched turned to hang.  Eventually I'd be staring at a spinning beachball.  After a few (five to ten) minutes, it might perform a couple queued events (opening a window, switching to another application) but would usually become wedged again immediately, forcing me to hard restart.
I then tried installing Firefox 5, and discovered that it causes the hang fairly reliably within the first ten seconds.  Since I knew when it was about to happen, I managed to capture a few stack traces in Activity Monitor, but it was always different, and always somewhere in the kernel (usually file-system related: __getattrlist while scanning fonts one time, the open system call another).
Safari, on the other hand, works great.
I've tried performing a verification of my startup disk, which returns no errors, so although I'm not ruling out hardware failure at this point the problem started immediately after I upgraded to Lion, and persisted even after I wiped my hard drive completely and performed a clean install from the recovery partition.  It also doesn't seem to be completely the fault of either Chrome or Firefox, since they're different browsers with different rendering engines using different system frameworks.  They do both perform a lot of file I/O, so maybe that's a clue.  Another possible lead is the seemingly random errors Console will spew out while the hang is occuring.  Most recently I've gotten a screenful of '--ImageKit Error: updateGLTextureWithBitmapData: glPixelStorei returned an error : 506 ...', and before that it was 'Google Chrome Helper: CGSLookupServerRootPort: Failed to look up the port for "com.apple.windowserver.active" (1100)', "kernel: IOSurface: buffer allocation size is zero".  Console spew being what it is, though, I don't know if any of that is relevant.
I figure I would be seeing quite a lot of angry forum threads if Chrome and Firefox were completely unusable on other people's machines, so I'm guessing there's something specific to my configuration happening here.  With a clean install, though, I'm not sure what it could be.  Here are detailed system specs:
24" iMac (Early 2008 -- just out of AppleCare coverage, figures) , 2.8 GHz, 2GB RAM, running Lion build 11A511 (which should be the 10.7 release version).
I would be massively indebted to anyone who has experienced or heard about this issue before and can give me something else to try.

Answer 1

Zeroing the disk serves no purpose in this situation.  It is a common misconception that this is required to map out bad blocks on the drive, but the fact is that 1) modern hard drives map out bad blocks as part of everyday operation, and 2) zeroing the drive involves simply writing zeros with no checks to see if the zero was written successfully, so it wouldn't know if a block was bad anyway.
It's possible the drive is starting to go bad, although then there should be some problems with SL as well.  I would recommend repartitioning the drive with Disk Utility.  Make sure it's got one partition, using the GUID partition map scheme, and format that partition as Mac OS Extended (Journaled).  Repartitioning should get rid of any gremlins lurking on the disk, unless the physical disk itself is dying.  And after repartitioning, install straight from the flash drive, as Shootist recommends, rather than installing SL first.
Hardware could be an issue.  It's entirely possible for an older system to work fine on slightly faulty hardware while a newer system does not.  Running Apple Hardware Test wouldn't be a bad idea.
Firmware updates wouldn't be a bad idea.  However, note that my mid-2010 MBP with the same specs is running Lion just fine, and I've never installed any firmware updates.  (Firmware updates scare me...  if my machine is running just fine, I'm reluctant to risk installing new firmware.  But that's probably just a bit of paranoia talking.  )