Here are some ideas:
- Isn't there a logfile somewhere the captures all the errors?
- Perhaps it's a permissions issue on one of the files?
- Maybe something wrong in the .htaccess file?
I'd have the hosting people look into it, they can't expect you to just put up with errors. It could very easily be a server misconfiguration isssue, in which case it is their problem.
As a programmer, it's hard for me to accept problems being the accepted status quo. Often times at my job, I've often discovered my customers had been putting up with very annoying bugs for years and years simply because it's "just one of those things the system does". They'd work around annoying things for years and never complain about it. But once we did find out, it was often fixed within the hour.