Apparently the error below from Zune is indicative of some sort of problem with your DRM data. The redirect is to KB 929642 which of course doesn’t list the error message, but it was a useful clue.
Zune encountered a critical error and needs to close. For instructions on correcting this error, open the URL below in a web browser.
On my x86 box which hosts the Zune software, C:\Documents and Settings\All Users\DRM is where all this stuff is. You can check by going to HKLM\Software\Microsoft\DRM and looking at the DataPath value. If you double click it, the registry editor is kind enough to decode the binary data to ASCII. The KB referenced above also has some info on where to find this folder on other platforms.
I simply opened a command prompt, renamed my DRM folder, and let the Zune software rebuild it:
C:\Documents and Settings\bdesmond>cd\
C:\>cd “Documents and Settings”
C:\Documents and Settings>cd “All Users”
C:\Documents and Settings\All Users>cd DRM
C:\Documents and Settings\All Users\DRM>dir /a
Volume in drive C has no label.
Volume Serial Number is F8EB-D584
Directory of C:\Documents and Settings\All Users\DRM
12/18/2007 05:44 PM <DIR> .
12/18/2007 05:44 PM <DIR> ..
05/25/2008 12:48 AM <DIR> Cache
08/06/2008 03:35 PM 3,739,648 drmstore.hds
12/18/2007 02:43 PM 1,536 drmv2.lic
12/18/2007 02:43 PM 1,536 drmv2.sst
05/25/2008 12:48 AM 1,194,512 IndivBox.key
12/18/2007 05:29 PM 4,867 migration.log
12/18/2007 03:53 PM 312 v2ks.bla
12/18/2007 03:53 PM 48 v2ks.sec
05/25/2008 12:48 AM 13,579 v2ksndv.bla
12/18/2007 05:29 PM 9,722 v3ks.bla
12/18/2007 05:29 PM 740 v3ks.sec
10 File(s) 4,966,500 bytes
3 Dir(s) 27,084,025,856 bytes free
C:\Documents and Settings\All Users\DRM>cd ..
C:\Documents and Settings\All Users>attrib drm
SH C:\Documents and Settings\All Users\DRM
C:\Documents and Settings\All Users>attrib -s -h drm
C:\Documents and Settings\All Users>move DRM DRM2
1 file(s) moved.
C:\Documents and Settings\All Users>