problem downloading files

Hi, I have problem on this page >>> http://soundgates.com/sg/documents/free ... re+Patches. I've created catalog with free downloads for logged users. Added custom field %free_download% but when I click download I get Internal Server Error
Is this related to spaces in filenames? If yes then what is the easiest way of fixing it - (besides changing the filenames and re-uploading ?)

also where should I upload .htaccess file with added additional file extensions so I can upload different types of files?

Thanks

Adam