So you have two copies of the commons-fileupload jar, which are different versions? The incompatible classes in those two jars are likely the source of your problem. Get rid of one of them and make sure you compile against the one you decided to keep.
Joined: Apr 16, 2011
Many thanks, seems to have fixed my problem.
I assumed (stupidly I guess) that having two, wouldn't mean none were found. But I guess a conflict would mean neither was used.