I also saw the bank/backpack mouseover/select problems following the 2.1 patch. I opened a bugtracker ticket since I was not the only one: http://www.wowace.com/trac/ticket/811
It appears that the layer ordering has changed in some way that affects some, but not all users. (I am running wow on Linux/wine - maybe a factor.) The workaround/fix for arkinventory is to add the frameStrata and toplevel tags to the item frame:
Line 442 of ArkInventory?.xml:
<Frame name="$parentContainer" inherits="ARVINVFrameStandard" frameStrata="HIGH" toplevel="true" id="0">
0
It appears that the layer ordering has changed in some way that affects some, but not all users. (I am running wow on Linux/wine - maybe a factor.) The workaround/fix for arkinventory is to add the frameStrata and toplevel tags to the item frame:
Line 442 of ArkInventory?.xml:
<Frame name="$parentContainer" inherits="ARVINVFrameStandard" frameStrata="HIGH" toplevel="true" id="0">