I've just exited the library in the tower of magic when I noticed this glitch (may be everywhere but this is the first time I noticed)
1) select all party members
2) Go into Cautious mode
3) open Cast Spell for a party member
4) Don't do anything with the spell, nor abort - just click to select all party members again, which will close the Cast Spell popup
Hey presto, I cannot click on anything any more (e.g. left click to move does not paint the circles or allow movement).
Fixed by leaving Cautious mode. Then everything works again, even if you immediately resume Cautious mode.
Can someone test this and see if it is universal or just some one off thing?