Rather dwnld the LW 4.0.8 version, why not dwnld the beta 4.1.5. It has a no. of improvements. I very happily use 4.1.5. If you're a pro user you can dwnld the pro version of 4.1.5 from your dwnld page (the link's at the bottom of that page.) Otherwise the general 4.1.5 version can be found here: http://www.limewire.com/english/content/beta.shtml It has often been a case that one version of LW suits a person's system better than another.

Reinstall the suggested newest versions of both (incl. 4.1.5 & iTunes 4.6) If the problems persists, then take murasame's advice.

For me, although iTunes & LW apps are on the same partition (OSX), I have LW's dwnld folder on a different partition. You'd find more iTunes options in the beta 4.1.5 than 4.0.8! If LW's media player is ticked (in LW's Preferences), it might be worth disabling it so iTunes has total control over the mp3's/m4a's (make sure iTunes is fully abled in LW's Prefs.) And dare I suggest it, knowing your lack of time, but deauthorise areas of work b/w LW & iTunes (manually change folder permisions using CMD+I.) iTunes itself has a deAuthorise comp. function under Advanced on menu bar.

Don't know if murasame's target has anything to do with iMovie, but be wary of it. It has forever been an unstable app. Yes it can affect other processes. I don't even bother with it any more (I use Apple's FCP & DSP. And was on both their forums.)