In my SUSE SLES 11 SP 2 there was a bug in PHP Version 5.3.8 that didn't allow for any uploads. You could use the same php-file I was given to test whether you have the same bug:
http://moodle.org/mod/forum/discuss.php?d=199754#p875791
I had to install the patches released a month after SP 2 was released to make it work.
Rosario