Hi all, I decided to have another try with reactive and got the basics working. I created a simple program that just beeps until a timeout is reached or when a key gets pressed. This works OK, so I wanted to take it a small step further. Now, I only wanted to stop if the 'q' key is pressed (or timeout is reached). I tried filterE, filterMP and the alternative definition of filterMP found in the source. I found that in all cases, one thread of the program immediately grabs 100% cpu and makes the program sluggish/unresponsive. I'm on ghc 6.12.1 and compiled without any optimizations. here is my example: http://hpaste.org/fastcgi/hpaste.fcgi/view?id=24810 (everything works when "stopper" uses "keyevent" but breaks on "qevent¨) Is there anything I can do to get the behavior I want? Thanks, Mathijs