Myself and someone else have tried the latest version of ZenseMe (1.1.5), and there appears to be an issue when it tries to scrobble to Last.FM. I didn't know the application got updated until the other day, so this was new for me.
Basically, it happens when the songs are already picked up from the Zune, and you hit the button that will trigger ZenseMe to start scrobbling to Last.FM.
I verified, and my login information is the same between both 1.1.2 and 1.1.5, so I'm not sure what's happening between the two versions that's different. Based on your change notes, I'm guessing it had something to do with the Last.FM scrobbing improvements?