Yes, that happens because without the competition port adapter, the OI's are defaulted to channel 40 and the other channel's are not avalible, to fix that you can either run one on a tether, or make an adapter for the competetion port, info on that is found on IF's site :
http://www.innovationfirst.com/FIRST...Operator_..._Guide.pdf

This problem pops up occasionally and everyone has pointed to their experience.
The cable between the interface (Robot side or operator side) and the modem can go bad after months of banging around especially if kinked. The modems operate at just above 900 MHz, in a band licensed for public use. (i.e. walkie talkies, home wireless phones, remote data links, security cameras.) Rough handling has occasionally caused some internal damage on either radio modems typically the antenna. If the cutout is occuring at regular intervals, check for things like a new weather radar installation nearby, aquarium heaters or wireless lighting controls in a nearby conference room or classroom. As a last ditch attempt, see if you can borrow a spectrum analyzer to monitor the band and see if there is anything present at the frequency of the radios. It will tell you if there is an interferring signal or if your radios are not generating signal.
Good Luck

It seems that many people are having trouble with the modems. Just be glad that we still aren't using the RNets (pre-2000) ;-)

We know it isn't rough handling, as Al suggested because it happens with all thier robots, including the EDUbot. I would think it is some type of interference, as other people suggested. The only way to find out for sure is to get a spectum analyzer as Al suggested.

2.4 Ghz
 

Perhaps it's time to move to 2.4Ghz, maybe even run the robots over WiFi or 802.11b. Instead of serial cables, use network cables.

Now thats the future... lets put all our robots on wi-fi. So anyone with a wireless card/laptop could mess with the robots. ( I'm sure someone could manage to do that with a Linux Laptop with Wireless card ) Of course only if it's standard wi-fi and using tcp/ip to talk to the robotics... Which I'm sure could be done with Java ran robots...

You think you have connection problems? Try testing you're bot in an Army research building. I have no clue what they were playing with, but it will probably give me cancer some day. Even worse, caused all kinds of trouble for the 'bot.

Thank god we got out of there!

-Andy A.