Sounds like a different problem altogther mark. The original poster had a connection, but thought it had slowed down: which it hadn't (the DSL part of it anyway). Now you can not connect at all, right?
So, what are we talking about here? Do you have DSL? or are you just connecting two pc's together?
It sounds like the cable to me: two pc's linked together without a hub or router would require a different type of cable: a crossover cable rather than a straighthrough cable.