Does the adapter have any trouble finding wireless networks and connecting to them right away?
Does this happen while you are actively using it or does it drop after being idle?
If this happens when being idle or computer goes into sleep mode, try disabling any power saving settings referring to USB ports. You may also want to check your BIOS settings on your computer to see if there are USB settings there. I know many people have issues when the computer comes out of sleep/hibernation mode. The USB port sometimes gets turned off and some USB devices have trouble waking up (thus unplugging the USB adapter and plugging it back it fixes it).
If it just randomly drops while you are say browsing the internet then there may be a hardware issue with the adapter, or maybe something with the router/extender working with the adapter.
Wi-Fi is VERY sensitive. Moving your router 6 inches can improve the connection. Make sure no appliances, metal, fish tanks, mirrors, etc are between the adapter and the router. Make sure both have at least 3 feet of clearance around the antennas.