General aviation pilot reported an aircraft communication equipment failure while in cruise transitioning special flight rules airspace under ATC control. The pilot returned to the departure airport and landed safely.

Narrative

The plane had just come out of an annual inspection. Everything was working correctly during takeoff from JYO and getting to the planned cruise altitude but then halfway through the SFRA; the PFD (Primary Flight Display) started to display flashing red Xs for the Frequency and Transponder page areas. ATC called on Guard and reported that my transponder was squawking 1200 and asked that I change it back to the assigned code and found that G1000 was reporting Transponder fail and the button for entering the transponder code was not shown. I was not able to enter the transponder code nor enter the frequency that I was talking to ATC on. I was able to contact ATC on Guard and explained what was going on. The Autopilot continued to work normally. After a few minutes the cycling red Xs on the display stopped and then I was able to reenter the assigned transponder code and reenter the assign ATC frequency and communicate with Potomac approach. I continued to fly out of the SFRA and then circled; back to JYO by staying out of class b and the SFRA until the JYO maneuvering area. The problem with the PFD did not re-occur. The shop was not able to get the problem to repeat. The shop de-mated; cleaned; and re-mated all of the connections to PFD. I suspect during that segment of the flight that some strong RF interference was causing the PFD to act up.