In my situation, there are 4 fields(textfield) and one for picture upload,which I use jspSmartUpload, in my jsp .
I can upload a picture if only one field,type="file".but when I put 4 other fields in this jsp .it can not works.
I use servlet to process the upload with jspSmartUpload.
maybe you should try Jason Hunter's MultipartFilter.
you can find the com.oreilly.servlets-package from http://www.servlets.com .
and I recommend that you also read Jasons article from javaworld ( http://www.javaworld.com/javaworld/jw-06-2001/jw-0622-filters.html )