I'm running GNOME 2.14.0 on Fedora (kernel 2.6.17-1.2157_FC5 if it matters) and the filetypes in .zip files seem to be picked at random. I can assure you that .o files are not Speedo fonts or Flash videos or Dia diagrams, nor is .cpp a Word document.

Steps to reproduce:
1) Download/open http://www.osdever.net/downloads/kernels/pk0-7.zip
2) Go to /pk0.7/source/kernel/ and look at the file types. (Sometimes it actually reports them correctly or as "unknown type". Just click the little "up" button and go back into kernel/ again, it should happen.)
3) Also try /pk0.7/source/object/ or /pk0.7/source/include/

Actual Results:
I get completely random filetypes and icons most of the time.

Expected Results:
The correct filetypes, duh :-)

Build Date & Platform:
Fedora (kernel 2.6.17-1.2157_FC5)
Not sure how to find the build date.