>>Well, asking for specific interfaces was one of the tricks to work around IE mangling the HTML, needed for the early versions, and makes sense from the errror you mentioned. But in your first code snippet nothing was done at document level ? Or left out ?
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>No, and never had to.
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>This worked well for a year. Then, a Windows update kicked in and never worked since then. A year after, I decided to investigate more on the issue trying to find a workaround. I hope his one will be good for a while.


Puzzling... Why did you create a new instance of IE in the first place for each navigation ? Back ages ago each process could .Navigate2() to a couple of thousand URL before WorkingSetSize started to inflate and had to be clobbered. You could check, whether a new default interface has been created somewhere in ShDocVW or MSHTML.

Back then, calling .Navigate() often was replaced by the newer (IE4, IIRC) .Navigate2(), but that should not result in an error.