This afternoon after work I went out to grab two photos of two different locations within 1/2 mile of each other.

The first one was a McDonalds that getting ready to get torn down to rebuild a new one, lots of power lines and busy street so I coudl not get a great angle (leagly) so I did the best I could, no problems.

Packed everything up and travel 1/2 mile down the road to take construction photos of a new hotel and started getting lost GPS messages, got spooked and did not get any good shots but did not like the errors popping up. Basically in the middle of a open field with no obstructions.

What could cuase this? Wasn't ready for any drama today....

There are no clues there.
Out in the open with a good sky view, you should have full GPS reception.
Have you checked since to see it it wasa one-off event or an ongoing issue?

Post your flight data and it might give some more information.