I have not seen that type of video problem for a long time in UFT on Win 9x, but would try "SafeMode" first. (Hold down F8 key on Windows startup). It is possible that some other legacy program, such as a kids game, has screwed up the video, and will continue to do so until you get it uninstalled.
You do have video memory card greater than 2/4mb and or screen resolution equal to or less than 800 x 600, don't you? Nobody has made any changes in the motherboard rom bios? Your bios battery (nickel sized) isn't dead is it?
One place to look for hints in Win 98 is win.ini. Also do a search for *.ini and see if some other program has modified video settings on startup. Then look to see if you have a Global Font Change on the Desktop or Win.ini that has substituted some oversize legacy font for MS Sans Serif, or perhaps Courier. Foxpro dos not take kindly to global font substitutions.
Then check your video and monitor device drivers to make sure that plug and pray didn't make a substitution on you. (including vertical refresh rates) If all else fails, turn off Video Acceleration in Windows>Display>Advanced.