Well, I was riding home this evening on my GPX, when I noticed my steering started to feel weird. As I continued along, I decided to ask my boyfriend to take a ride on the bike to see if he could find the problem, (he has been riding for over 10 years). Then, as I took the last few corners before reaching home, the steering felt worse and I slowed right down to feel a little safer. Once I pulled up at home, I got off my bike to look for the problem. I checked the front wheel and forks, no drama there and then I looked at the back tyre, ah ha I said, that explains everything. One flat tyre=very unhappy me, especially since I had only bought the rear tyre on Tuesday. I'm glad I was so close to home when it happened, as I have only been riding for 17 months and had not experienced anything like this before.