The MS05-026/896358 security update that Microsoft released two weeks
ago is probably responsible for this. You can read more about this
here:
http://support.microsoft.com/? kbid=896054
The solution should be to use one of the “Method 2” workarounds
described in this article to remove the block on help files in the
Local Intranet zone. For example, you could try saving the following
text to a file called “MaxAllowedZone.reg” and then running this on
your machine.
REGEDIT4
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\HTMLHelp\1.x\ItssRestrictions]
“MaxAllowedZone”=dword:00000001
> Also I noticed if I download any new help files from the internet they don’t
> open correctly either.
This is another consequence of installing the 896358 security update.
See the following article for advice on how to unblock downloaded
files:
http://support.microsoft.com/? kbid=902225
—
Pete (Microsoft Help MVP)