All of you who upgraded from Windows 7 or 8 to 8.1 please try the following:
Go into Device Manager. You can do this by right-clicking This PC in Windows Explorer and selecting Manage then find Device Manager within Computer Management container.
Find Network Adapters in Device Manager, then locate your wireless device (this will be Broadcom, Intel or other brand 802.11n or 802.11a/b/g/n or something similar).
Right click on it and select Uninstall. Check the checkbox that says to remove/delete drivers completely.
Proceed with uninstall then restart your computer.
Upon restart your wireless adapter should be reinstalled with the driver that comes with Windows 8.1 and this driver should then work fine.
The reason is, apparently after you upgrade from previous Windows version the driver does not get replaced automatically with Windows 8.1 driver so you have to perform the above procedure manually.
I experienced the exact same connection dropping issues and this worked for me.
Oh, and btw, when you get it working do not install your manufacturer's drivers if not absolutely neccessary.
HTH
Interested to know date of the Microsoft driver for 8.1. I occasionally get drop outs now, so I must have fixed the main culprit that was causing problems when I first upgraded, but I cannot remember if I upgraded driver.