I'm guessing you guys are using the iphone fw on ipod... that's what i had and all my DRM songs wouldn't play. Until yesterday, I did the proper ipod fw and jailbreak, then everything is okay now.
first what are DRM problems?!
and secondly i went from 1.1.1.jb to 1.1.2.jb and than to 1.1.3 jb
now I recoverd to original 1.1.3 gonna try tomorrow again, and tell about if i have the same issue.
If you went from 1.1.1 to 1.1.3 you will have DRM problems.
You can check the installation shell script to see if it was using iPhone's or iPod's IPSW ... or... you can ssh into your ipod and see if Phone, SMS apps are in there... if they are, you are probably running iphone fw.