Problem with Spiky Rocks

[Riccio]

When I cast Spiky Rocks during a combat,the game terribly slow down as the graphic effect of the spell starts. Almost a frame per second.. I tried to play again using the same save a few times it was like stopped in the end.. the third time I could slooowly finish the combat.
Uff I didn't manage to upload the files, however in different games I had the same problem.

Ops, wrong forum, delete...