[Zope] pdf files dont work ??

[bdorn@vup.at]

hello all

i've a python product class which inherits from "file"
now if i upload a few pdf files (~1MB) and i try to view them with the 
browser and this doesnt work with all instances

the browser loads something but it doesnt start acrobat reader, it 
displays an empty window
i set the content_type to "application/pdf"

i read somewhere that the id has to end with .pdf - so that acrobat 
checks the file - but this wasnt the problem

is it possible, that the files are too big or corrupted ??
because sometimes it works
there is only a problem with .pdf files - with others like word files it 
works just fine even if the file is 800kb big.

would it be better to store such files in the filesystem instead in zodb ??

please help - thanks in advance - bernd