Say, on this subject i did the same thing, two installs with different prefix and cookie etc. in one mysl5 database and did have an issue with the old board skipping over to use the new boards tables even thought the prefixes were quite different. It was crazy weird...but not too consequental as I was done migrating my settins over and closing the old board. Just some weirdness. It suddenly said it had the new prefix for it's tables in the cp. The only thing I did before noticing this change was to use the drop down on the old board to change the skin. It still had the old header html I put in but the new cp settings!
