Fix for stackable potions
32 Bit systems: http://pioneerontheprairie.com/sylvanheart/PotionFix_32bit.exe
64 Bit systems: http://pioneerontheprairie.com/sylvanheart/PotionFix_64bit.exe
Right click on "Computer" in the start menu (or "My Computer") and go to properties to see if you have a 32 Bit or 64 Bit system. Note that you may still have to tell the fix where to install. It needs to install in the place where you installed UO.
Enjoy,
~ Admin Cypress