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I had a Logitech G9 and my mouse kept disconnecting/reconnecting after a few seconds randomly. So I changed back to my MX518 and didn't have the problem for at least a month. Then it started again. Right now I just had a disconnection/reconnection every 5 seconds for an entire minute.
I've looked into Device Manager and everytime the disconnection was happening it was refreshing. I tried turning off the power management off all the USB Root Hub. I don't know what to do anymore.
Here's a screenshot of my device manager :
EDIT: And I've also tried the mouses on other computers and they work fine. I'm on windows 7 64 bits.