Garmin 590 Issues - Help Needed

[Snowbird]

Probably the cold start thing, the sats are never quite in the right position as they change orbit over time so if not used for too long the gps has to try and get a fix with no idea where the sats are, once it has a link it downloads the latest almanac which is like a list of corrections so it knows where the sats actually are rather than where they should have been, once the gps has that info it should get a fix much quicker, without accurate almanac data the signals may not make enough sense to work out it's position.

You didn't really want to know any of that now it's working again did you.

Disclaimer: I'm a greasemonkey not a navigation expert so all the above could be complete b*llocks but it's how I understand it to work.