Summary: It appears that someone forgot to remove the "Old Version" link in Google Analytics, when you access it through Adwords. With the "Old Version" officially retired a few weeks ago, the link just loops you back to the Analytics home screen.
As you likely already know, Google Analytics launched a new interface last year. To allow for a smoother transition, Analytics kept an "Old Version" link at the top of the screen for anyone who wasn't familiar enough with the new layout. This was helpful when you just wanted to grab a couple of quick metrics but you didn't know where to find them inside the new version yet.
The GA "Old Version" link remained until April when it was moved to the footer. Presumably this was done to nudge people toward using the new version. Many people, myself included, felt forced in to the new version at this point because at first glance it seemed like the link had been removed all together. It was definitely a great transitional step for me, and I imagine many others, because just a few weeks ago Analytics finally killed the old version completely... though it seems not everyone at Google got the memo.
Today, while I was doing some Adwords campaign management for one of our PPC clients, I used the helpful direct link over to GA from Adwords, when to my astonishment I saw the ghost of Analytics past:
Now this wasn't exciting for me personally because I forced myself to learn the new Analytics interface after they hid the "Old Version" link in the footer, but it certainly seemed like news worth breaking.... until I clicked the link:
That's right, clicking the "Old Version" link (after accessing Analytics via Adwords) just takes you to the main NEW version screen you always see when you first log in - the account list home screen. As you can see, the "Old Version" link is available still on this screen, but it just keeps opening the same screen in new tabs no matter how many times you click it.
So is this some sort of cruel prank to taunt users who still pine for the old Google Analytics? That seems unlikely. I think Google probably just didn't have a thorough QC plan in place for removing "Old Version" links, and because the Analytics and Adwords teams are separate entities, I suspect the Analytics team isn't even aware of the issue. I've tweeted them, but who knows if they'll ever see it!