I have been having an issue with my MacBook for over a year and I just figured out the solution. JiWire was causing the problems all along. Let me explain my situation in case it is helpful to someone else. About 12 months ago I began having problems with my wireless connection. My throughput speed would fluctuate making it impossible to use things like iChat or Skype. When downloading a file using the wireless connection the download speed would peak for 2 seconds, then drop to zero or near zero for 2 seconds, then peak for 2 seconds, then drop, etc. etc. etc. over and over. I couldn't figure out what was causing the problem. I took the MacBook in for service and they replaced the wireless card and I thought that fixed it but the problem reappeared not too long after the repair. Some times the problem would occur soon after turing the computer on and other times it would take quite some time before the problem occurred. Well .... tonight I installed OS 10.5.3 hoping that it would fix the problem. After the reboot everything seemed fine for a little while and then the problem "mysteriously" reappeared. I tried rebooting the computer and it was fine for a while again and then reappeared. I was checking the system temperature using the iStat Pro widget to see if there were any changes in the system temperature. Then I realized that the wireless throughput problems would appear after I would turn on Dashboard. So ... I decided to turn off one widget at a time to see if I could figure out what was causing the problem. The first one I tried was JiWire and when I turned it off the wireless throughput was PERFECT (WOO HOOOOO). So ... what was happening was, I would reboot the computer and then it would work fine until I had a "peek" at Dashboard and JiWire would turn on. Then the wireless connection would become buggy and I would reboot. Then it would be fine again until I had another peek and Dashboard. I didn't put 2 and 2 together until tonight I have tried turning JiWire on and off about 20 times to make sure it is the culprit and, sure enough, ever time I turn it on I begin having problems with my wireless throughput. I feel like such an idiot of putting up with this for a year. I can't believe that the solution was as simple as turing off the buggy JiWire software. I did a search of the forum for JiWire and I found the middle of a thread that mentions this issue. This may or may not be the solution to your wireless problem. I hope that this thread is helpful to someone else. I can't imagine that I am the only one that has been having this problem. I'll report back later to confirm that my problem has been permanently solved. My fingers are crossed!! Cheers.