Am assuming that you are using SafeStrap. If so, boot to recovery. Go into boot options and activate the "stock" slot. Then, if you want to, you can go in and delete rom slot that you have beans installed on.
Once you activate the stock slot, you'll know it because it will tell you with red text across the top of the screen.
Then just reboot.
IF YOU INSTALLED BEANS ROM ON THE STOCK SLOT, you need to download a copy of the stock odex or deodex rom that beans put together in the dev thread. If this is the case, let us know if you need help before going any further!