I think I found a solution. Initially I based the method of adding registry entries according to the IE version on the one that BlackWingCat used in his Security Rollup (JPN only). I thought that if he's used it in his Rollup, then everything would be O.K... but it proved that there is a flaw in that method. While all files were indeed copied properly (IE5 files if IE5 installed, IE6 files if IE6 installed, etc.), the registry entries for each version of IE/OE were not added at all!
I had to add one section to the update.inf file which I found out about when analysing the update.inf from Update Rollup 1 (official). This is just technical information for anyone interested in modyfing updates
The old one was like this (just a part of update.inf)
Operation=CheckFileVer, browseui.dll, >=, 18.104.22.168
CopyFiles=IE6.System32.Files, IE6.Cache.Files, IE6.VGX.Files
CopyFlags=SP_COPY_NEWER_OR_SAME | SP_COPY_REPLACEONLY
but this is not enough to have the "AddReg" and "DelReg" sections properly processed. An another section must be added:
Only after adding these strings the registry entries are 'activated'.
This post has been edited by tomasz86: 28 June 2011 - 05:18 AM