[Zope] Limited File object size?

When uploading a file to Zope I am getting an error about commit_sub. I uploaded some other files to the same folder but am having problems with two in particular. He only difference I can see is that the others where 10k to 60k and the two problem files are 100k and higher. Is there a limit on the file size that can be uploaded or is there another explanation? TIA Stuart