http://www.kongregate.com/games/undefined/quick-quests
Xp, Turns, potions... 4byte*8

Works fine for me.  100% stable.  I'm using Cheat Engine v5.6.1 w/Firefox 6.02.

I start off choosing the appropriate plugin-container process, then look for turns, 500*8=4000, doing a 4byte search twice - once now and again after turns decrement.  I then freeze the address at 40 until I'm bored.  Repeating the process for Experience points, I set the address at 4000000; each battle will increase the character level by 1.  You can skip this and go straight to tweaking the character level but I think you may miss out on bonuses incurred through incremental leveling.

Remember to always use increments of 8 when entering your new values.  Unless you know the limit of the variable, don't go wild with huge values.  If the game remains unstable when you try to tweak it, check that you are using the latest Adobe Flash version.

Browser crashes because of cheat engine are usually caused by changing values to a number that is not a multiple of 8 (or a multiple of 8 + 6) or by freezing a value on a game where the address changes every level. Your problems were probably caused by the former, and definitely not by the latter, because the addresses do change the same each game.

This game is at least more original than most of undefined's games, but damn it gets boring fast, and even faster if you cheat. I don't really see any point in cheating at this game unless it gets badges, which most of his games do.