I have a server's network shares mounted as local drives using fstab and smbfs. I download NZBs for news servers directly to the local drive (network share) and the files corrupt. If i download to a different directory then copy to the drive all works well. However, if i create a local shared folder to download the NZBs to mount them on the server as a drive everything works ok.
Here is my fstab entry
//steve-server/NZBs/ /media/NZBs cifs guest,uid=1000,iocharset=utf8,codepage=unicode,unicode 0 0
Please try to add -o directio to the mount command. This is very likely a duplicat of bug 6898.