Starfox: Would you happen to have an ATI HD4xxx or HD3xxx card with Catalyst 9.5 or 9.6?
I just discovered this morning after installing the new Catalyst 9.7 on my HD4850 that Overseer crashes in the exact same way you describe. And it's not the only game either. The support for Thief 1 and 2 is completely broken since Catalyst 9.5.
I don't know what the drivers team at AMD/ATI intend to prove but they apparently thorougly screwed the support of several old games (prior to DirectX 8) with their HD series of cards.
Catalyst 9.4 works fine though. To this date it's the last set of Catalyst drivers that works fine with old Windows games (at least as far as Thief and Overseer are concerned).
This solution works for people with 4xxx and below, but my 5xxx card has this issue without the luxury of rolling back to driver versions that far back (9.xxx drivers). This is still an issue, and definitely not resolved.