Yes. As a matter of fact, you should know that uploading a file takes a lot of time depending on your connection and the file size. A PHP script exceutes itself and dies in 30 seconds by default. The problem is that it will upload only 2MB in 30 seconds.
Before executing your upload script try using this little code:
set_time_limit(0);
That is going to make PHP make the script last until it is finished uploading.
This feature is not documented and gives a lot of a headache to people, but 99% i've seen this, is because of that.
Hope it helps you
fLIPIS