Hi there,
Generally anything odd that goes on (lost shelfs and such) is down to preferences, deleting them, estarting maya creates a default prefs folder that generally solves and problems.
I remember once, god knows what I did, but I created a script that when run stopped Maya doing anything, and I mean anything, it started than did nothing! Deleted the prefs and it worked.
"No pressure, no diamonds" Thomas Carlyle