Weird problem with double click using trackpad button and wireless mouse

Macbook (white one) OS 10.5.6.
Mail 3.5, ical 3.0.6.
The double click function does not work in mail (try to open a message), ical (insert an event) and iphoto. I can use cmd + O or file/open (mail.) Does anyone have any ideas? It did work when I got the computer (in May).

Wireless mice are not created equal so that one is hard to answer without info.
Trackpad checkout Sys Prefs/Trackpad for selecting features.