Messed up Wiper?

Hi

I have a 1995 C280 and its been raining a lot here in Dallas lately. The windshield wipers havent' been working right on my car as of recent. I thought it was just the wiper blade because the wiper arm was getting "hung up" slowed down when it reached over the center of the winshield. It turns out the wiper blade was bad and I did replace it, but the whole mechanism still gets hung up sweeping over the middle area of the winshield. Any ideas as to what would cause this? Could the motor be worn out? The blade swishes water away, it just gets caught in the middle of the winshiled and struglles to reach the other side and sweep back arounda again.

Thanks,
Troy