CAn't Post messages or upload files

[Kusco]

I don't know what happens but in my forum i could not post messages, or upload files, if I do that with admin permissions, if i do that as normal user, i can, and as admin i can approve posts....
I verify the permissions for admin and its ok,

The message I get is

Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator, <a>webmaster@treinodesportivo.net</a> and inform them of the time the error occurred, and anything you might have done that may have caused the error.

More information about this error may be available in the server error log.

Apache/1.3.33 Server at treinodesportivo.net Port 80


anyone could help me, Please...