http://im.qq.com/tt/images/release/testpage.html
just happened upon a page that tests a certain memory leak problem in the Trident engine, and so far it affects all versions of IE (including IE8 beta) and Trident shell browsers, except two :

Tencent Traveller, the Trident shell who made the memory leak test to promote itself
http://im.qq.com/tt

MiniIE, a Trident shell that has a custom garbage collector
http://miniie.com/

unfortunately they are both in Chinese.

So a browser shell actually can fix something wrong in the engine

It depends on how "fix" is defined. Browser shells can certainly work around some problems of the core. But a work around is good only if it can apply to general/common scenerio rather than specific tests.

well, it seems the garbage collector of MiniIE is working quite well for the general/common scenario, it actually claims itself to be THE grapical browser that uses the least memory. I'm not sure how accurate that claim is, but so far it does use less memory than Firefox, Safari, K-Meleon, and Opera, which is quite a surprise for me. I never expected the Trident engine can be this memory efficient when there's a custom garbage collector.

The Tencent Traveller also uses significantly less memory than IE, on par with Opera.

I assume it "fixes" the memory leak by stopping it from ever loading in trident? (same way other shells "fix" things by changing stuff around before the engine loads it)

Or are they doing some odd in-memory patching to the engine to fix the code?

Sleipnir deals with those kind of leaks. The memory usage climbs but drops back to normal when the tab is closed.

Website in Engrish

http://www.fenrir.co.jp/en/sleipnir/

well, with MiniIE and Tencent Traveler, the memory usage doesn't climb in the first place. (and in non-Trident browsers like Firefox and Opera, the memory usage also doesn't climb at all)