Mower stalls when blades engaged after replacing mandel?

Replaced mandel on LGT2654 Husqvarna. Worked well for a while. Grass extremely high, so took it slow. Mowed the normal height grass, than tried to slowly mow the tall grass again now mower stalls when blades are engaged. We took the blades off and checked the blade assembly and it engaged as if the blades were on, so we replaced the old blades with new ones. Started the mower and tried to engage blade assembly. Mower stalled. What could it be? Is it possible that the mandel zerk needs lubed?

Julie
May 2010