Weird! I've opened a ticket here:

http://scratchexp.media.mit.edu/issues/329

I cannot reproduce this in IE8. The IE7 VM is taking a ridiculously long time to log in, and I'm still downloading the IE9 VM. I'm not even going to bother trying it in IE6.

EDIT: It logged in! (after like twenty minutes!)
EDIT2: Setting up personalized settings…
EDIT3: Yay, it's done doing…y'know…whatever Windows Vista does.
EDIT4: And now IE7 is taking forever to launch.
EDIT5: Ooh…set a network location for “Network4”
EDIT6: UAC.
EDIT7: IE7 finally launched!
EDIT8: …And I need to restart *facepalm*
EDIT9: Windows is shutting down…
EDIT10: Windows is starting up…
EDIT11: “Please wait…”
EDIT12: “Welcome”
EDIT13: Three minutes after I was welcome…a taskbar!
EDIT14: Ohdeareverythingwentwhite!
EDIT15: Back to normal(ish)…launching IE7. (IE9 part 1 is 83% downloaded)
EDIT16: Microsoft Security Essentials makes an appearance! (IE9 part 1 is 91% downloaded)
EDIT17: An IE window! (In other news, Microsoft Security Essentials makes another appearance. IE9 part 1 is 94% downloaded)
EDIT18: Hm…MSN worked fine but my local IP doesn't… (IE9 part 1 is 98% downloaded!)
EDIT19: “There are multiple problems with your computer.” Oh dear. Good thing it isn't my real one. (IE9 part 2 is 25% downloaded)
For the record, this mess is one of the many reasons I prefer OS X.
EDIT20: Ah. My hypertext browser wasn't smart enough to put http:// in front of my IP address.
EDIT21: Hm…we're missing a space, but let's move on (IE9 part 2 is 93% downloaded!)
EDIT22: I forgot to log in. (IE9 part 3 is 24% downloaded)
EDIT23: I don't want Internet Explorer to remember that password. No. Grrr. (IE9 part 3 is 42% downloaded)
EDIT24: There are more unrelated issues with this site in IE7 than I have fingers. One of them is apparently on line 3, character 3, of the HTML file although that seems a little impossible. (IE9 part 3 is 67% downloaded)
EDIT25: I looked it up, and most of the errors are caused by trailing commas in the JS files. Fun. (IE9 part 4 is 15% downloaded—when do these things end?)
EDIT26: Surprisingly, posting something worked perfectly. No alerts, no errors. I cannot reproduce this in IE7. (IE9 part 5 is 51% downloaded)
EDIT27: I found some trailing commas… (IE9 part 6 is 25% downloaded—make it stop!)
EDIT28: Oh, there are seven parts and the last one is really small. Almost there (IE9 part 6 is 69% downloaded)
EDIT29: We went from 17 errors to 15… (IE9 is all downloaded—now we're extracting…)
EDIT30: The IE9 VM finished setup! Time to run it…
EDIT31: Hey, it booted in less than ten minutes!
EDIT32: Or not…
EDIT33: Logging in…
EDIT34: More “Personalized Settings!”
EDIT35: A taskbar!
EDIT36: Launching IE9…
EDIT37: Launched IE9.
EDIT38: The site looks beautiful, and posting worked fine. No error messages, and no dialogs. I cannot reproduce this in IE9.

I'm almost 100% certain this is a cache issue.

Edits much?

Huh, i just got it clicking search. I hadn't even typed anything!

You need to clear your cache. No force-reloads; just get rid of it entirely and see if that helps.