I can't find any other post relating to this problem but apologise if I've missed it. I bought my wife a 405 the other day but we can't get it to hold a charge. We've been on the Garmin site to download a fix for it, but the program isn't seeing the device.
There is an alternative to all of the sweetners containing aspartame etc, Xylitol.
Xylitol is a naturally occurring sweet tasting substance that looks and tastes just like sugar. It has 40% fewer calories than sugar and can be used in cooking (not jams/marmalades). It has a low glycaemic index and can be used by diabetics. Its sold under the names "perfect sweet " and "xylobrit". Its used a lot in chewing gums as it is good for the teeth.