Sharepoint - SharePoint 2010: Open with Explorer disabled on specific library
After a lot of digging around and asking other administrators, the only answer I can get is just "It's broken, abandon it." This is unfortunate but I was looking for an excuse to restructure this particular library anyway, because it's growing so fast that it really should be split up into multiple libraries just because of the sheer volume of data it contains (it went from 4GB to 25GB in about three weeks!).
Thanks to Dave Wise and ppatalong for their contributions, and thanks to David Lozzi for suggesting a clever work-around. For anyone who didn't see, the work-around was to map a network location to the library, or to open another library in Explorer and then navigate to the one in question.
If i come up with any other solutions I'll post them here.
Cheers!