my emergency brake light keeps coming on everytime i shift in 1st and 2nd gears.why is it doing this...

my emergency brake light keeps coming on everytime i shift in 1st and 2nd gears.why is it doing this. Lately its beginning to do it in 3rd gear too.

2006 scion tc
40,000 miles
manual transmission

when i shift my car from neutral to 1st gear, or from 1st to second gear; the emergency brake light on the dashboard comes on as the rpms get around 2500-3000 and then it goes off when i shift up to the next gear.  It doesnt really do it in 3rd (although it has happened a few times) and it has never done it in 4th or 5th.  I'm going to take it to the dealer to get it looked at but i was wondering if maybe you guys knew what could be causing this.  Is it something serious or just some computer malfunction thats no biggie?

thanks

bruce