The RPMS won't rev if the engine is still warm, if it doesn't rev after sitting overnight, then that's not normal. Sounds to me like almost an eletrical problem with the trans relay if swaping them fixed it for 2 days.

Time to break out the voltmeter and get a service manual off these forums for the wiring diagrams and make sure you're getting power where it's needed and that there are no shorts. Still not going to rule out any problems with the tranny itself, but I'd focus on the relay and the wiring first because it's a free fix if there is a problem.

 

I have the same error code, only when mine starts to flash I lose 1st gear also.... It only happens intermittenly but when it does Its always when I have been driving it for a bit. My Trans was rebuilt in AUG 2010 and it does have a 12 mon warrenty to but the shop said they have already replaced the Shift Solniod A once and checked the wiring and everything things fine... only it doesnt SHIFT like it should all the time!

 

update: I have drove my D for about 400 miles now after swapping the relay with the horn(I swapped the fuel pump relay back) and hasn't thrown a code yet.I guess relays get weak? We'll see what happens.

 

The relay pins might have been dirty, but it is possible for the coil in the relay to overheat and get weak, rarely.
Hopefully that was the real problem all along.