I'm not sure if it is the same issue, but I just created a URL link in the wiki, (using the HTML Link button) and it's not possible to save the wiki page after that. It just says "Saving", with the spinning balls, but nothing happens for at least a couple of minutes (after that I've gave up and closed the browser window). There's no problem saving normal text.
All in all it looks like the Wiki implementation is pretty immature at the moment. A guess an alternative would be the MediaWiki addon, however that doesn't seem to be working with Labs 3 Stable (3.1).
Edit: In my case it was a browser-related problem, it works as supposed in Firefox and IE, but not Google Chrome.