Interesting, I would suggest checking your globalization/regional/lingual settings in CRM, in Excel (File->Options->Language), in Windows via the Control Panel, and the database Collation settings (SQL Server Management Studio->Databases->yourorg_MSCRM -> right click -> properties->Options->Collation).
I suspect that these strange characters are the result of some mismatch in the text encoding between these products.
Good luck, I hope this helps you find the cause and solution. Let us know what you find.