Just how waterproof is the 3500 supposed to be? Mine gave up after 3 hours in the rain on Sunday. There is now condensation inside the screen and it will not switch on. Any suggestions as to how to solve this ? Will it work once it has dried out ?

aquapak come to mind
as for working again 50/50 at best, dry out very slowly
Waterproof (IPx7) rating = Protected against water immersion - Immersion for 30 minutes at a depth of 1 meter.

so where do we get this aquapak from & does it work with the unit rigged up to m/Bike

http://store.aquapac.net/ I use my 3500 kayaking so very waterproof
....and can't be used on a bike, if you want a waterproof GPS get a Garmin

Get a returns note and send it back. Its advertised as boasts an IPx7 waterproof rating

FYI a very similar thing has happened to me. I took my 3500 for a 4 hour walk in the Lakes, during most of which it was in my jacket pocket. Got back to the cottage to find the 3500 non-functional with water dripping out and condensation behind the screen. As suggested above, have contacted support for a refund.