Last night I was testing my map with some friends, and they reported that they didn't see any of the localization changes I had made. Everything showed up fine on my screen though.

I was running the server using swbf2sm 1.1, with the 1.3 patch and Bryant's exe, and everyone had the most recent munge, including the server.

Any idea what's causing it?

Edit: It just occurred to me that my friend doesn't have 1.3 installed on his new computer, and I had changed the addme so it would have a custom map name color/mode name/era name. Would this cause issues with loading core.lvl for people without 1.3?

I was about to ask if your friend had 1.3. I'm pretty sure that's the issue.

People without 1.3 have problems, and people with 1.3 have less problems.

v1.3 added the feature of changing the game mode and era names on a per map basis. The stock SWBF2 doesn't support that.

If you're referring to unit localization, than that's an annoying problem with SWBF2's localization and is related to which language version of SWBF2 they installed and which v1.1 patch they're using (if any).