I too have BU353 running under W7 (but 32 bit) without problems but David has had a bag full of frustrations. I suspect a conflict of drivers somewhere or some Windows registry problems but how to find out what is really happening in his system by remote
diagnostics would be a big ask. Happily he has solved
his problem with a different GPS. Just the fun and games of an OPEN system such as the PC/Windows combo. Personally, for my on-board system I am going to use a Ubuntu system with the BU353 and virtually nothing else connected or running to try to keep some of these variables under control.