The most current firmware version for the Slingbox M1 is 1.0.082. The link directly below shows what firmware you should have for each model of the Slingbox:
I would start with uninstalling and rienstalling the Slingplayer for Desktop 5.0. If that does not help, you may need to hold the reset button on the Slingbox for 10 seconds. Below are a few links to help you with those steps:
Hope this helps!