Been having some very odd issues on the Mac Mini 4,1 system I have. It looks like the mouse started to play up, and oddly enough new batteries never changed the issue. Soon as I removed the ram, and put back factory memory. It all came good. It’s safe to say the 2 x 2gb modules I got have some issues. Think I will bin those, as they had no warranty.
It looks like Other World Computing (macsales.com) has some great prices. Might order from them some replacements.