It could be that the op is being forced to disconnect to allow data for the dictionary attack to occur, however as Ed mentioned, using a random password with WPA or WPA2 is enough
I also agree that MAC filtering is useless and probably dangerous, giving a false sense of security :
http://blogs.zdnet.com/Ou/?p=43&tag=col1;post-127 , number one in the list of six dumbest ways of securing a wireless network.
I use a 32 character randomly generated key and keep it on a USB key and transport that between computers while setting them up. It's worth noting that a ten character password would take 400~ years to crack with a single PC. Never use christian/surnames either as keys since there's plenty of dictionary lists that have comprehensive coverage of names.
http://www.yellowpipe.com/yis/tools/.../generator.php is a WPA key generator if you don't feel random enough ~