If you would, please provide a little more information, It might help us help you. Which version of RealFlight are you using, and what type of interface?(InterLink, wireless ect) When you open the "launcher", look in the upper right Quadrant of the window, for the specific version (like 7.50.011)
Has this been a problem, since install, or something that has developed, since some change, to this program, or in your system.
Does the menu bar disappear completely, or does it "loose focus" and become inaccessible?
Are there any other issues you've noticed, like not being able to use reset (interface button, or space bar)
A few DIAGNOSTIC TESTS you might try, is, change airports, and see if this brings menu bar back. CAN you toggle between full, and windows mode, if you can, does the menu come back then? Try temporarily disabling your antivirus, and see if this clears up the menu issue. Please report back. Helping you, solve your issue, may help solve, someone else's.