I'm going to make some assumptions about your file and you tell me if I'm right:
You're trying to parse a Office 2008-generated file
It's a file with Chinese or Japanese characters in it
OR it's a file created on Vista
If so, S::PE probably doesn't handle something correctly. If so, create a minimal testcase and send it to the author. He's pretty good about fixing stuff quickly.
My criteria for good software:
Does it work?
Can someone else come in, make a change, and be reasonably certain no bugs were introduced?