(new user) Unable to save any file including .xcf

[Montmorency]

Brand new Gimp user here, using 2.10.2 on Windows 7, 32 bit.

Installation went very smoothly.

Opened a relatively small existing jpg (photo), less than 100kb probably.

Managed to use one of the basic guides to convert image to a pseudo circle.

Then tried saving to .png, but the save dialogue just "hung".

Tried to save to .xcf, but that hung too.

Restarted gimp, and after reading around, realised I should probably be exporting as, rather than saving as.
Did that, but it also hung.

Restarted again, and just tried saving as .xcf. Hung again.

Restarted again, and now I couldn't even open the .jpg, or any similar .jpg.
The open dialogue hangs in a similar way to save.

I assume there must be something wrong with my installation of Gimp.

Only thing I can think of is to reinstall.
(Maybe I should reboot first - haven't tried that).

Thought I might be memory constrained, since this box only has 2GB, but these are small files I'm trying to work with.

Should I try an older version, perhaps? Where would I get that from? I didn't see any options for older versions on the download page.

Thanks a lot in advance for any advice.