I have a 60C and have the same lockup problem.
I live in Quebec and I get a lockup at many places.
This will happen with City Select V6 and Topo Canada maps loaded.
On Highway 640, north of Montreal, I always know where the GPS will stop....
I also contacted Garmin and they told me to return my unit but I did not do it since I was sure the problem was with the firmware.
I told them that the problem may be with the french language or with the multi-map features.
I went back to 3.30 and everything works fine.
I hope Garmin will correct this bug soon... so I may have the newest features.
Martin