Hey guys, i currently run a forum and been having problems for over 1 month

i currently have a server admin but hes kinda busy doing his stuff..

i know a little about server managerment and hopefully u guys can help me

i have a invision forum.. 2.1.X
IPB Version v2.1.7
SQL Version MYSQL (5.0.30-Debian_2-log)
PHP Version 4.4.4-9 (cgi-fcgi) ( PHP INFO )

the problem is, everytime i post a new topic, it gives me a 500 internal error, however the post comes through but its causing alot of users to double post....

i have had chmodded everytihng to 755...
dun know what else to do.. steps would be great.. also i will be happy to pay anyone who will help me solve this....


cheers