Have you checked our FAQ's ?
Q: ProFlight 2000 won't start. All I get is an Overflow Error 6 message
A: Somehow ProFlight has allowed a change to one of the following settings to an incorrect value, resulting in the overflow error message. If you open the PF2000.CFG file and scroll down to the FlightInfo section (almost at the end of the file) you will see three entries as follows:-
CruiseSpeedIAS=238
CruiseSpeedMACH=0.74
CruiseSpeedTAS=420
If you check these you will probably find one or more of the values to be very high... Eg. A cruise speed of 4000 would obviously be incorrect. To correct the problem simply enter a correct value and resave the CFG file... then restart PF2000. We are currently unsure as to how these values get changed... PFE most certainly does not change any of them... so if you discover how to recreate the issue please let us know.