One solution would be converting it to NTFS from within Windows (unless you have a power failure it's totally safe, there's no data loss, I've done it myself a few times) then install Macfuse with the NTFS-3G driver, or use Paragon NTFS on the OSX side to have full read/write.
Personally I wouldn't trust a 320GB FAT32 partition anyway, the filesystem was never designed for disks or partitions of that size.
You could also try dividing it into three partitions, maybe a 320GB FAT32 partition is freaking Chameleon or OS X out. There are some tools that can do it without data loss, such as the venerable Partition Magic 8.
It sounds like it could be a bug in Chameleon though. It could also be intentional for some reason. Either way hopefully someone will appear and explain it, I'm curious too.