After installing the surreal theme people using 4.5 beta on some BB device have been getting "reset error 523". Fixing this reset error is a piece of cake, all you had to do is connect your device to the computer, get to the cmd prompt where you have javaloader saved and type, javaloader -u erase -f net_rim_theme_surreal_320x240_b.cod
This will remove the theme and restart your device, no need to re-install os or erase the device.
I can write a little bat file to help if you are stuck.
By the way, you can use a similar approach if you get this error after installing some new apps/themes. Just erase them using javaloader.