Google Favorite Icon is "SD" instead of "G" in MSIE

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I now get the letters "SD" in red in a small black box as the favorite
icon when at a Google URL. I also have some significant hangs
sometimes in MSIE when bringing up Google Advanced as well as
sometimes when using the back button on various pages.  Google seems
to work normally and I have no other signs of infection on the system.

Other user accounts on the same system work normally. There's nothing
in any startup keys in the registry or elsewhere that I can see.

I assume I must have some sort of malware... Does the "SD" indicate
something specific? What's the next step to diagnosing?

Vista, SP1

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