Hi,
I have just had the same problem today.
Synapse popped up saying that there was an update ready to be installed so i went ahead and did it, the installer asked for a reboot so i did that.
After restarting the mouse did not work at all when plugged in several ports windows did not even recognize that a device was being connected!
FIX:
1) Find a temp mouse and uninstall razer synapse 2.0 (ensure that you unplug your deathadder before doing this)
2) reboot your computer
3) Go to razer website and re install synapse 2.0 and do any necessary updates ensuring your death adder is still unplugged!
4) reboot your computer
5) once windows has fully loaded back up and synapse has started ensure no more updates are needed then plug your Deathadder back in!
If when you plug your deathadder back in an update pops up unplug the mouse install the driver (restart if prompted) and then plug the deathadder back in.
This worked for me however if you don't use synapse and you are having this problem it is possible that the mouse if faulty.
If you don't use synapse and have this problem,
Go to device manager, expand the mice and other pointing devices menu, right click any mouse related drivers and uninstall them. Restart your computer with the mouse plugged in and windows will re install the driver (windows 7 or later)
I hope this helps anyone with a similar problem.
Thanks