Strange ALT key behavior running c4droid on my droid 3
Since this behavior appear only in the c4droid app ,it isn't a system problem but a problem with the c4droid app ,I suggest you send a feed back to the app's dev ,the implementation of supporting physical keyboards is in the app it self ,or may be there is an option in the app's settings to remap or choose keys behavior.

Email address of the dev: n0n3m4@gmail.com

C4droid's Play store Page