i encountered the same http 500 error on a site i co-wrote.. however it was not because of a code error,
it occurs from time to time, randomly when users browse through the webby.
good thing it is not frequent however, i checked the error log files but it shows nothing but the occasional missing files (images),(html).
but it might be a nuisance since the site is a e-commerce site.
i'm totally puzzled. besides the occassional 500 errors the site runs fine.
i did some lookup on google. commonly it says mis configuration of the apache bla bla...
i left them at their defaults however, no htaccess mods anything except for a timezone changing php code in my script...
what could go wrong ? does distance from the server has impact?
*edited typo*