hmmm, I've used that same BB before actually, no problems though. Maybe pull it out and re-grease, make sure you get every metal contact point, ex. where the bb shell slides into the cups as well as the threads.

The tollerances of the bb shell into the cups it very tight so make sure you get it everywhere, a lot will be pushed out.

People always say "Don't grease square taper BB axles" saying it will damage it. But put a little on anyways, it will be just fine trust me.

When tightening the crank arms back on remember, with square taper, you don't want to torque it on super tight, this will do more damage to the axle than any grease will.

When you test it out ride in and out of the saddle, could be the seat post/seat rails as Toolshed said also could be the stem etc