Re-loading saved 744X flight not very good under Vista

I saved my mid-Atlantic flight overnight using the FSX Flights Save/Load option. Now when I load the saved flight, the aircraft initially climbs strongly from CRZ at FL290 to around FL305 and the speed sags to M.787 with a commanded speed of M.840. The thrust mode indicator is blank, and cycling A/T ARM has no effect.Then tried to step climb to FL330 (OPT FL338 MAX FL380). Aircraft began to climb but got no further than FL297 before settling there. Tried VERT SPD of +500 to encourage it, and this worked until FL327 when the VERT SPD blanked as normal. Then aircraft dithered either side of FL327 with achieved speed draining away to M.783.After 10 minutes, the aircraft had slowly achieved FL330 but speed now M.738 and slowly draining towards the shaking stick. N1 commanded 90.9.Very frustrating after a long cruise. Will try a save again overnight.Cheers, RichardPS one day I will get to KSFO!