Cut and paste issues

I have just upgraded to 1.5.3 for Windows, running on XP. I am writing in what I take to be the default, “Courier New | Regular | 12 | 1.0x”. When I cut and paste the font re-emerges from the paste as “MS Shell Dlg 2 | Regular | 11 | 1.0x”

This is irritating. What is the cure?

Moderator note: Locked for being a duplicate. Link to duplicate.