500 Internal Server Error

Sorry, mod security made the error with Internal Server Error. After I open for mod security, all is working...

I uploaded the file, and everything works fine, BUT...
After the file was uploaded I got an error page...
Joomla 2.5.20

2 problems:
1. When I use ex 95,5 in a colom it comes as 95 after uploading.
The database table is varchar(255)

2. After uploading I get this error:

Internal Server Error

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

Please contact the server administrator, This email address is being protected from spambots. You need JavaScript enabled to view it. 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.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.
Apache/2.2.26 (Unix) mod_ssl/2.2.26 OpenSSL/1.0.1e-fips mod_bwlimited/1.4 mod_fcgid/2.3.6 Server at student.gse-schools.com Port 80

What can be the problem here?
Thanks!