what I did to fix this was camp out of game.
Then go into notepad or your favorite editor and open the character's ini file, found in the Everquest2 directory.
ie:
Guk_Depechenode_eq2_uisettings.ini CORRECTION--> Guk_Depechenode_eq2_uisettings.XML
Scroll until you see: <Module Name="Inventory" window_version="36">
then look for the first line starting like this:
<Window Name="Bag_clone_0_-3" alignment="16" alig.......(long line)
Select that line and everything under it until you see:
<Window Name="Bank" alignment="14" alignment_offset="-78,-65" locked="true" size="531,166" />
DELETE everything you selected but NOT the last line mentioned above.
RELOG into EQ2 and (yes I am sorry), reset ALL bags, bank, inventory..any bags you have, all slots. Then CAMP.
Log back in...and voila FIXED.
Previous theories states only deleting the odd bag_clone_255 etc, but I found this does not work.. What I described does work. I used it and my bags are staying placed/sized every log on.
I hope that all makes sense, easier to "speak instructions" rather than type them out
-dn