"Just wanted to relay my experience regarding the kernel panics with a Mac Pro (1,1) upgraded with quad-core Xeon 5355's and ATI Radeon HD 4870 graphics card. After upgrading to Lion I started getting Kernel panics about every couple days. After doing some trouble shooting and having no success, I remembered that I hadn't tried resetting the PRAM. Once I reset the PRAM the problem went away and I haven't had a problem since. Don't know if this will work for everyone but it's certainly the easiest fix.
-Ron"

I know some said that didn't solve the problem for them but it's easy to do and worth a try. (The later rom of the first Quad-Core mac pros of course may have other fixes/benefits perhaps and I completely understand those that updated to the 2,1 bootrom feel it was worth the effort.)
 (Resetting the pram/nvram is an old troubleshooting tip that goes back decades and is still listed in OS X Help. It clears some (user/preference) settings stored in nvram however and may lose the startup disk setting (if completely/properly cleared), so use Option key at boot if need be. OS X Help has a note on that w/RAID volumes.)

Update: (Not sick of this topic yet?) One of the readers (Khai) that had originally said the 2,1 rom helped just wrote that he's switched his boot drive from his HD (Lion upgraded over SL) to a clean install of Lion on a Vertex SSD and his KP problem is back. (Long story but booting from the old HD Lion install still ok he said. More details to follow later.) Just another example that problems and/or fixes are rarely universal. (And there's an almost infinite number of hardware/software config and hdw state variations possible.) Some of course never had KPs to begin with, even with same Mac Pro model, 1,1 rom and quad-core cpus.
Here are a few questions (off the top of my head) I have regarding his KP's:

• Are the KPs random or repeatable/related to any specific task/function/app, etc?
  (Earlier notes IIRC indicated it wasn't a case where the system would KP at every boot)
• Does the drive check OK? (no corrupted files/prefs, etc - chk from another boot HD if reqd)
• Any useful info/error messages in the logs?
• Are temps OK?
• Are no KP's seen even in stress tests/heavy use when booted from the "ok" drive?

Another basic TS tip is to simplify the equation (i.e. disconnect any unnecessary devices, remove/disable any 3rd party addons if possible) Other general tips were mentioned in the first post on this Sept 19th. (I'm sure they're not news to anyone here.)

  

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