I've run into this problem a couple of times and, even though you've already bypassed it, I thought I'd throw in my two cents.
My working theory right now, is that it's somehow related to how Impulse is plugged into the overarching "how windows does internet" structure. I almost never use IE, but when it doesn't work, this particular window in Impulse also doesn't work. I've seen a similar issue in steam, where the integrated browser doesn't work sometimes. I typically reinstall IE at that point, and everything works fine, for a while. I imagine it's something simpler than that, and that my "solution" is all sorts of overkill, but it couldn't hurt to check.
