I rode my bike home a couple nights ago and realized I couldn't access gears 5-8 on my bicycle. The shifter would work, and I could see that the cable was pulling. When I shifted to 5 the pedals would lock up. I shifted through all the gears many times on the way home and determined that gears 1-4 were fine. Has anyone had this problem before? Is this problem able to be fixed? Will I ever be happy again?