Frederico did send a message some weeks ago about a new memory leak in IE7 that it was becoming a pain as it isn't documented anywhere else and it could consume lots of memory if a page contained several instances of FCKeditor.
So he has posted a reply to the IE blog that suggest us how to use the existing tools to find the typical leaks. Some people have confirmed the problem (while others just see a reference to createPopup and have to give their opinion without bothering to test the proposed testcase)
As he has asked now for new confirmation of the problem I did a quick test and it worked fine for me, there was some slight increase over time in sIEve or Drip, but nothing so spectacular as the 1Mb per reload that he stated, so talking on the IRC channel for FCKeditor we tried to find the differences as we both have tested in XP SP2 and none of use have any special toolbar that we could blame.
Frederico confirmed that he didn't see the big problem in sIEve or Drip, but for me everything worked correctly, maybe something like 1Kb.
Then I remembered that usually there's one thing that I've done to all the IE7 installations because I never use it for surfing and the anti-phishing icon annoys me, I don't want to be distracted because a web that I'm developing hasn't been checked. Yes I know that it's safe, I'm coding it!
So I went to the advanced preferences and enabled it and OMG, now every reload of the page in IE7 took more than 1Mb of memory!
Unfortunately I don't think that too many people disable the anti-phising filter completely and just turn it off so they still suffer the memory leak.
If you want to check this, go to Tools -> Internet Options -> Advanced and scroll down to the bottom, you'll see something like this: and the solution to the memory leak is to switch that option to select the "Disable Phising Filter"
Now that the origin is clear, can we hope for some kind of fix in IE? or are we hopeless like the rest of IE bugs?