Yes I battled with the WSOD for quite some time. I tried those previously posted suggestions in vain:
-I went ahead and updated to the latest version of Word Press (2.6.2).
-I deactivated every plug-in as recommended.
-I even cracked a beer in frustration
However I DID find a solution. One huge variable in site design is the theme. Posting comments seem to work wonderfully when I switched to a more common/standard theme such as "WordPress Default" amongst others, while would predictably give the WSOD on other less common ones such as "Cloudy".
Not surprisingly the code for properly posting comments is basicly dependent on 2 files (one of which is theme related). The first of which, located in your primary WordPress installation directory, is called "wp-comments-post.php". The second of which, located in the directory of the theme being used, is called "comments.php" (not rocket science, eh?). Knowing that the theme "WordPress Default" had a functional "comments.php" file I simply copied and pasted it into the "Cloudy" theme directory (overwriting the troublesome original). Ta Da!
After thorough testing of my site (using the now modified Cloudy theme) I've found it to work beautifully. And yes cracked another bottle of the sauce.
I'm sure that would explain why, dear friends, a clean reinstall of WordPress wouldn't necessarily fix your problem. An engine overhaul and a new transmission will never fix a flat tire... or maybe it would in both cases if you did it 5+ times ;-)
I do know that the complex web of variations in plug-ins, posts, permissions, and WordPress versions on any given project can make things a shade unpredictable, but the point is keep trying different themes until you find one that works for your setup starting with the most common/default.
Best wishes and happy tinkering!