WebDAV Mac OS X issue 2.2.6

I can not authenticate a user using Mac OS X 10.5.5. Anonymous access will work for reads, but I can't do anything that would need authentication (create folder, copy image etc.). WebDAV works just fine with the same user under Windows XP. What is odd is that the Mac appears to be appending /mach_kernel to the path when it pops up the dialog box for authentication. I see a bunch of PROPFINDs in the apache access log including one for mach_kernel. Regular WebDAV access from the mac to apache for non gallery folders works just fine (and I've tried turning off mod_dav and that didn't change anything). Any other suggestions?