The 64-bit client seems to have consistent issues with tracking meta-key state (ie. SHIFT, CTRL, ALT/Option, command), meaning it seems the client gets confused on KEY-DOWN and KEY-UP events. When the client gets confused, things like:
- The mouse will stop sending events to the client (probably to another window).
- Keybindings with the meta-key will stop working.
- Spells will get stuck in the half state (ie. target for the ground but cannot then initiate the spell).
- Mouse binds will become odd (like, left mouse will stop working and right mouse will be run).
Hitting random meta-keys repeatedly until it goes away will fix it. And easy way to reproduce it is use the following keybindings: CTRL-1 to CTRL-5 to map 6 to 0.
The 32-bit client has zero issue with this arrangement.