Outlook underlines words I know are spelled correctly!

This is a strange one.. Outlook 2007 is underlining in red words that I know are spelled correctly, for example:

Many thanks for your email which arrived at the University just before our Christmas break so I do apologise for the delay in getting back to you

It is absolutely bizarre! I have checked the settings for proofing and autocorrect etc, and as far as I can tell, they are just the same as a colleague who is not having this issue.

Is this a known issue? Does anyone have any ideas? I've been Googling, but it is so tricky to put this into words that a search engine will understand - I just get pages and pages of people with the exact opposite problem.

It seems to me that a 64 bit outlook express is installed in your computer/laptop and hence the spell check isnt working the way it should be. So, try running msconfig and click on the "Expand One File from Installation Source" box and type csapi3t1.dll in it. Now select the "i386" folder named from the windows location to restore from. After that just enter the name of the folder to send "csapi3t1.dll" when prompted. The name of the folder is "C:\Program Files\Common Files\Microsoft Shared\Proof." Click "Expand" to send it to the folder and restart the pc and check if it works.