What OS do you have?
Can you give more detail about any error messages or log messages you're seeing?
What is the speed of your DSL/Cable/whatever connection? How much traffic are you seeing when you have problems? – James PolleyDec 29 '09 at 12:11
It might be that you're maxing bandwidth in at least one direction on your link. If you have in fact done this, any packets from your MSN/SSH connections could be taking so long to get across the connection that your end (or the other end, depending on which direction is congested) gives up waiting and times out
It might be that your router simply can't handle so many connections, and is losing track of older connections