"New Tab" freezes opening link in 32-bit Explorer on 64-bit Windows-7

The title says it all.

When running 32-bit Explorer on 64-bit Windows-7, right click a link and select "Open in New Tab", a new tab opens, tab caption is"Connecting...", but it never connects and the tab response to nothing other than a close.

64-bit Exporer works fine.

Anyone any ideas why this happens?
Thanks

P.S. To forestall the inevitable questions, we need to use 32-bit Explorer to test our own sites that rely on 32-bit controls. This has nothing to do with this problem, it shows up with general browsing.

Folks, sorted with help from an answer to a (sort-of) related question on serverfault.com (which I no longer can find).

Registering ieproxy.dll fixed the problem, assuming similar setup to my own, run

regsvr32 "c:\Program Files (x86)\Internet Explorer\ieproxy.dll"