At my work we bought a bunch of the wireless mouse 6000 and a few notebook 7000 versions about a year ago. I liked the 6000 so much that I bought one for home too. So far two of the transceivers at work stop working after a few minutes and the same thing
happened to the one at home. Its like they heat up and the electronics fail. The mice with the broken transceivers work fine with working transceivers so its easy to pinpoint the issue.
I have always loved the Microsoft line, due to ergonomic reasons, but this is just poor engineering. If the only option is to buy a replacement mouse it will certainly not have the Microsoft brand on it.