Hi Ronald,
You didn't mention what version of DSpace you are using (and if it's 6.x or below, which User Interface you are using). The answer here depends on which version of DSpace you are using.
You also didn't mention whether you are receiving an error from DSpace itself, or what the problem is that you are seeing. Uploads obviously can be impacted by not only DSpace, but also your internet speed/connection, and even firewalls or similar.
If you are receiving an error from the User Interface, I'd recommend looking at our troubleshooting guide for information about finding the underlying error in logs (as sometimes that underlying error can provide more information on the root cause):
https://wiki.lyrasis.org/display/DSPACE/Troubleshoot+an+error
Please share this information on the mailing list, and hopefully someone can provide more specific help once we know what version of DSpace you are using, and what errors you may be seeing.
Tim