That mso9.dll file is called a dynamic link library and is part of the huge number of these items included in Microsoft Office. Occasionally these library files get corrupted, producing errors like the one you have encountered. The mso9.dll apparently is particularly prone to getting corrupted, and it usually causes troubles in PowerPoint, Word, Outlook rather than FrontPage. There is a way to repair such corrupted files in Office; here is the drill:
Click on Start and Search and then Files and Folders. Use the search term mso9.dll, and when you find it give a right mouse click and rename it something like mso9.fix. Now all you need to do is persuade Windows to restore a repaired version of this library file using the Start/Control Panel/Add-Remove programs command. Select Office in the Add/Remove list and click OK. This brings up a prompt to use Maintenance Mode to Repair the mso9.dll file.
In the unlikely (I hope) event that you don't find relief forcing the restore, you can always go back and rename mso9.fix back to mso9.dll and you'll be back where you started.
Hope this helps.