I just repeated this exercise - but without deleting my profile - but
this time installing 1.5.2.
I had the same problem -- BUT I'VE TRACKED IT DOWN.
I nomally open BG from a shortcut on the taskbar.
When I opened it from the exe file directly the problem disappeared.
It looks as if the shortcut (which I didn't re-create because it was
there already) is saving some archive information.
After deleting and re-creating the shortcut the problem does not
recur.
I reckon it is a bug. Shall I report it on Bugzilla?