Hi Alex, you dont have to be in LNAV.VNAV, not sure why someone suggested that. Check your FS settings, you may have switched it from indicated to true airspeed by accident.
Edit - Actually Mike makes a good point. That fsuipc issue has been reported here before. Will do a search to find that post.
http://forum.avsim.net/topic/423246-really-struggling-with-the-t7/page-2?hl=%2Bfsuipc+%2Bflaps#entry2846918
@Mike - normally whenever this issue with fsuipc comes up, the users aircraft is flying nose down as it struggles to climb. The OP doesn't seem to have that problem
Regards