Summary: Searching the internet, I found this is actually a fairly common problem with logitech and the G400. Tried many of the proposed solutions to no avail. It was a great mouse until it broke, but I still think I should have gotten more out of it for $50.
Pros: Awesome Mouse. Fits into the hand great. The sensitivity settings on the top are great in case you want to make quick adjustments. Thumb buttons are nice.
Cons: While I initially thought it was pretty durable, this one only had a three year lifespan. It frequently has a problem where it will not work when the computer is first turned on, and disconnecting and reconnecting will just cause it to reconnect to the computer over and over for about 10 minutes.
Summary: Love the mouse. Love the side buttons. Very comfortable. Too bad it started shorting out after a year. It constantly disconnects and reconnects. This is my 2nd one, wish they would last longer.
Summary: I like the shape and the texture. It functions really well when new. Problem is (as many mentioned) this particular mouse doesn't seem to be very long lived. Most mice I have owned, from cheap generics to expensive name brands, have lasted many years with no problems.
Summary: I bought two of these in 2013 - one for use at work and one for use at home. The work one gets used routinely while the home one very seldom and sporadically. The one at work is great, but the one at home just stopped working. Reason?
Summary: I got the G400 cheap, but I much prefer the G500 with the third thumb button and the fast scroll clicker. Both are pretty dated at this point, but they have basically the same shape, and it is worth the cost to get the extra features of the G500.
Summary: Had this for quite some time, broke after 1 year of use due to the infamous cord problem. Tried to get a replacement from logitech but the mouse was never sent to my address. So I googled it, bought a mx518 cord off of ebay and used that. Now it's been working for over 4 years.
Summary: I'm personally a fan of Logitech, but this mouse has given me a lot of issues. I currently have a wireless model coming soon. If that gives me issues as well, I might have to bail on Logitech...
Pros: Bought it due to good reviews, worked well for a year.
Cons: Has a life span of a year. No more. I called in warranty for the first one and got a free replacement in 2013. It's 2014 and same issue again. (Mouse gets power but it no longer responds in x or y). (It is not a driver related issue)