For numerous weeks i wasn't able to scrobble any tracks of my ipod what i hated. I did try all solutions and none worked. A friend found out a solution which works at both computers, so hopefully it helps with more people cause I understand the annoyance.
First make sure that when connecting ipod itunes starts up automatically. Then connect your ipod before you start up your computer. After start up and itunes has been loaded go to your last.fm icon, go to diagnostics (via help) and to scrobbling. Put it on manually and start scrobbling. You will probably get only errors but after a little while you get your pop-up of the plays you had. After that i put it back on automatic and close it (dont have to wait for full manual cause it might take some time, mine does)
Solution for scrobbling issues