why is it that the signal keeps dropping out when using the dwa-142 with the DIR-655
Well, this could be caused my many things. Wireless interference or just a corrupt driver installation. You can eliminate wireless interference by placing the router in a higher location in the room. You can remove close wireless devices such as telephones/baby monitors/etc. You could change the wireless channel being used (The most common are 1,6,11). You may want to re-install/upgrade the wireless adaptor drivers. All of which are on support.dlink.com.
why does the dwa-142 fail to see any wireless signals when upgraded to version 1.30 firmware
Interesting problem. You can try removing the drivers completely and installing 1.30 again (Rather than 'updating'). What wireless utility are you using? Are you getting a message other than "No wireless networks found in range"? You may have a 3rd party wireless utility taking over (Dell: Intel Proset utility/Dell WLAN connection utility. HP: Access Connection Manager. Sony: Smart-wi utility must have WLAN enabled, etc, etc).
why is it when using the wireless side of the d-link you get so many "server not found" messages
Well, I wish I could give you a specific answer. Perhaps if you tell us how often this occurs and when (Right when you turn on your computer? etc). Server not found is just a message saying you can't view a website for some reason (obvious, I know hehe). You might want to reset IE, delete cookies, etc. Do you experience the same issue when using another browser?
I'll check back here if you respond.
Best of luck,
-Russell