744 VC FPS dropping after a while

Hi,Encountered 744-v1r10 VC slowdown events recently:1) start w/good FPS (2D, VC, ext)2) RJAA to KLAX (and EGLL to KSFO) trips using ASv6 3) fly at econ alt according to FMC, 4x sim rate on/off for in a while4) around Alaska, VC FPS droped to around 8, stable at 85) 2D and ext FPS still high and stable (>40)6) cut sound, windowed or full screen, VC FPS stays low7) AP/AT on/off, quit ASv6, clear weather (using FSIUPC)--no change8) save flight9) resume saved flight--VC FPS back up to normal10) no issues until landingI don't know if it's the new weather or something, but it's weird. No HDD activity observed and task mgr didn't show anything out of ordinary. Seems to only affect the VC view.Has anyone observed something like this? HNYPatAMD A64 4000+ @ 2.6GHz, Zalman7700Cu cooler, Corsair XMS 1GB DDR, LTK6800GT-OC, Asus A8V MoBo, WDRaptor10KrpmHDD, TrackIR4, CH FSYoke + TQ, XP-hsp2