Problems with Fileupload

Hi freaks, my image library isn't still finished yet, but it's running and with a running system are comming new problems up. I remember that there was a discussion about big file uploads. It seems, that i stepped into the same trap, 'cause my web- server doesn't accept more than two uploads each upload session. I wrote a script which should make it possible to upload 10 files at a time. The files are up to 3 MB each so I had to set up the upload_max_filesize in php.ini to an amount of 50 MB Data. But it seems, that there still can be uploaded about 5 or 6 MB in two files at a time. Would be nice if somebody could tell me about made experiences. Thank you very much. Sascha Braun