Hi Doug. Thanks for the reply. Other suggestions were going nowhere, but when I read your bit above about looking in 'Where To', I went onto that and clicked it and then 'Geocaches' was there!! so problem solved.
I still dont know what happened though. I used to just switch my Etrex on and Geocaches would be there on the first page, I swear I never used to have to go through 'Where To' first, so I'm still puzzled but at least I can get into it now, so although you didnt mean to, you have solved my problem. Thanks !