Error on users page: preg_match() [function.preg-match]: Compilation failed: missing terminating ]

I've installed Location on a site I'm working on, and just added a location field to the profile content type (via Content Profile and CCK), and while things initially seemed fine, when I went to admin/user/user just now, I got the following error in a red box at the top of the page - 13 times in a row! (by which I mean that the error appeared 13 times in the box, not that I went there 13 times)

warning: preg_match() [function.preg-match]: Compilation failed: missing terminating ] for character class at offset 6 in /[path to modules directory]/location/location.module on line 942.

This error doesn't seem to appear anywhere in the issues queue, or at least did not come up when I searched for preg_match(). I checked the file location.module, and line 942 is:
if (preg_match($string, strtolower($name))) {
Which has no square brackets anywhere in it, and doesn't look like it should require any. The line in question is part of the function _location_autocomplete(), and I don't even know why that function would be being called on a page that's just a listing of users - there are no editable location fields being displayed on that page.

When I tried creating a sample profile, where the autocomplete fields were showing, I didn't encounter this error - why would I be getting it on a page with no autocomplete fields?

Any light anyone could shed on this would be much appreciated.