I've been experiencing two issues lately, let me briefly explain them to you:
1 - Cursor Disappearing
Every now and then my cursor will disappear from the game screen and will not come back until I completely close the game window and open it again. I've noticed that it has a chance to happen if I switch windows, like browsing and whatever while battling.
A good info on that, also, is that it has to do with the game cursor itself (the little wand) and not the Windows cursor. When that happens, and I am in the middle of a battle (meaning I cannot restart the game while I don't finish it), I put my laptop on sleep mode and then get back.
As sleep mode won't disconnect me from the game (if I do it quick of course), once I get back the cursor of the game is replaced by the windows cursor itself, which allows me to select properly my cards. It's just a temporary solution, as it will stop working if I minimize the game window (when I return it disappears again).
2 - Card Stuck on the Scren
Though the last patch notes have said it was a fixed issue, it's still an ongoing issue that needs to be looked into.
With the disappearing wand cursor, during battles you can get it back by slowly moving your mouse and watching until you see one of your spell cards getting 'highlighted.' It will pop out a little. Even though you can't see the cursor, it's there. As soon as the card pops up a little, freeze your mouse and click! The wand cursor will reappear.
I don't think hardware cursor is on their part. I haven't ran into that issue. As for the card getting stuck just click escape and hit quit then rejoin the game.
As for your cursor, I encounter this problem during battle as well. I play around with the clicking mechanism, however, which seems to bring it back up. As for the card issue, I am not sure how this came to be, but I do know that if a card randomly pops up on your screen, simply opening your bag and closing it solves this problem!