Blackberry wireless synch is freezing.

I am working on an issue for a user with a 7290. When we set up blackberries we let the blackberry synch with lotus notes first. Then, we change the setting to blackberry wireless synch. At that time during the next synch it goes thru the handheld calendar entries, out of 137 when it gets to about 115 it starts to move slow as molasses sand when it finally gets to 137 of 137 it freezes there. I let it sit for 2 hrs. it never came out of it. I am using desktop manager 4.1, which is the version that the company wants us 2 use. Any ideas.