I had the exact issue listed with SQLite3.dll, on Win 7 64-bit after the iTunes 10.4.0.80 update, and solved it as described by abbasfromdubai above (in the constructive posting, not the rant), though I actually got the fix via:-
https://discussions.apple.com/thread/2387547?threadID=2387547&tstart=0
which is dated April 2010.
Like me, you might be disappointed that Apple haven't got this right yet, even after more than a year.
However, I note that your similar issue, @grahamfromluton, is with libxml2.dll, not SQLite3.dll
libmxl2.dll is in my C:\Program Files (x86)\Common Files\Apple\Apple Application Support folder, but not in my C:\Program Files (x86)\Common Files\Apple\Mobile Device Support folder; but I don't have your issue with this file, so I can't tell what good, if any, copying it over will do.
(NB: use Program Files (x86) on 64-bit WinOSes, but just Program Files on 32-bit ones)
However, for the avoidance of doubt, can you confirm it was libxml2.dll you copied over? And if not, try copying that file over, and seeing if it fixes things.