The map screens:
There is no fix currently available, but there should be soon.
Crashin' Jack is working on a version of 1.28C which uses 1040x768 selection screens, and it displays the maps properly. It also seems to fix the screen tearing problem that some (1.2) 7217 victims get with 1.28b/c. Several people are awaiting news regarding the release.
"Pixellation" on the other screens:
A workaround for me is to select multiplayer...tcp/ip..then click Cancel when the IP entry box appears, then Esc to return to the mainscreen. For some reason the mainscreen then displays correctly.

Jel