Transmission Problem

I have a 1996 Honda Accord 2.7 liter with an automatic transmission. I have 173,000 miles on it. I have not had any problems with my transmission until now. This morning I started the car and put it in drive, gave it some gas and it didn't move. I put it in 3rd gear, gave it gas and it didn't move. I put it in 2nd gear gave it gas and it moved. At a stand still, my car will move if I put it in 1st or 2nd gear. It won't move in 3rd or Drive (4th gear).

After I get up to speed in 2nd gear, I can change gears up to 3 and 4 while moving. I'm sure that's not good on my transmission, but I had to make it to work. I checked my transmission fluid level and it looked ok. Could this be a simple inexpensive fix, or something serious?