Big Bugs in Logs

The fact that you have a 'historical database' on your 305 indicates that you have a LOT of past workouts on there?  If so, that is probably the problem.  Firefox is fully supported but the process works the best with the fewer stored workouts you have on the device.  If you can eliminate a lot of your older workouts and try again and let us know how it works.  The swim should not be moving to the bike column...let us know if this happens again after you have eliminated some old workouts.

"3- Stored workout limitations
If you have a lot of workouts stored on your device, the upload process may take a while. This was designed to upload only the data absolutely required, but if you have 6 months worth of workouts on your device and the upload process seems slow, you should look at deleting some workouts from the device.

*We designed this to be efficient and quick. Pulling off the whole workout history and working with it in the browser, or uploading it to the server could get problematic and/or slow if there are a lot of other sport workouts or a bunch of long workouts to go through."

See more on uploading help and problem solving

I've experienced the same thing.  The issue isn't with the BT code, it's with the 305 and Garmin Communicator.   The memory on the 305 isn't unlimited, so in order to keep recording workouts as it gets full, the unit degrades data on older workouts. This degraded data can apparently cause problems when it's processed by Communicator.

You have to regularly delete older workouts from your 305 in order to be able to efficiently upload them. I usually delete anything older than one month.