You're actually running 1.80e. SDC had a bit of a fluke where it treated 1.80e as 1.80g (and thus set the registry key as 1.80g). I'm not sure that's exactly how it happened, but as far as I can tell it's functionally identical to the current situation, so we should just be able to proceed from there.
If you change the registry key Version in HKEY_LOCAL_MACHINE\SOFTWARE\Stardock\Drengin.net\GalCiv2\DarkAvatar to pretty much anything other than 1.80g, it will properly recognize that it is outdated and running SDC will update you to the -real- 1.80g. I've found typing in 1.7 works fine, and is nice and simple as well-no need to mess with letters, even.
You can access the registry by clicking on your start menu, going to run (alternatively you can get here from task manager, via the file menu-some systems are configured not to have a run box in the start menu) and typing in "regedit", without quotes. This launches Microsoft's registry editor, and you should be able to navigate yourself via the folder tree from there.
Someone wrote up a very concise, straightforward how-to for this here
-my wording is a bit clumsier, I think. This thread
might also be useful.
Alternatively, if you don't personally feel like mucking around in the registry, you can simply use this
. It's a .reg file that will change the Version string to 1.7 for you, and will work on all versions of Windows from 98 up until XP, and it should work on Vista but I haven't had the opportunity to test that. You can open it with Notepad/Wordpad/etc to verify the contents, and feel free to run it through whatever virus scanners you may feel is necessary. It's clean, and it does exactly what it's supposed to-no less, no more.
Your last option, other than the above, would be to uninstall DA and then reinstall via SDC, although apparently this has not worked for at least one person, for some reason.
As an addendum, do be sure to switch over to the US-1 server if you haven't already-the US-2 server is apparently trapped in a bit of a temporal vortex. (Not literally.)
Hope that helps.