1999 Oldsmobile Alero Security light and dead gauges.

While driving the Brake, Security, Battery and Service Vehicle Soon lights all come on and all gauges drop to 0 as if the car had been switched off. The engine is still on and the car drives normally, just without any indication of speed, engine RPM, temp or fuel (the fuel gauge didn't work before so I'm not too concerned with this one). I can clear the computer by disconnecting the battery and then it will drive fine for about 20 minutes once the battery is reconnected, then it starts doling this again. My mechanic hasn't dealt with this exact problem before but believes it to be an electrical fault. He advised me to check all my connections, especially the main power line to the primary fuse/relay block. There was a bit of corrosion there, I cleaned it off and so far it hasn't happened again but I don't want this to happen on my 1 hour commute to work. A little direction on possible causes and solutions please.