Corrupt backup archives

I’m having a strange problem when trying to extract the home directory within my Virtualmin backups. The backup extracts fine on my server, but on Windows 7 (64bit) the tar of the home directory is reported as corrupt by WinRAR. I tried using 7zip and the directory structure is broken up into a bunch of numbered directories.

I tried creating tarballs (using tar and gtar) of the home directories through the command line and those archives work fine, but I’m not sure what parameters Virtualmin uses, so I can’t mimic Virtualmin’s process.

I suspect it’s some flag passed to GNU tar for incremental backups.

I have this problem on multiple servers I am running.

OS: centoOS 5.4
Virtualmin: 3.75.gpl

Thanks for any help or direction on this.