Suppose you try to upload a file and keep getting server errors thrown in your face. Have a look in the apache error log and see if you can find a line looking something like this:
mod_fcgid: HTTP request length 136872 (so far) exceeds MaxRequestLen 131072
If that is the case, then you are in luck. To fix it, look for the apache configuration file called
/etc/httpd/conf.d/fcgid.conf and edit it. All you need to do is add the following line at the end of the file.
These are the details for Centos 6, but for other operating systems it should be something very similar.