>>I don't think the method runs asynchronously (nothing in the docs to indicate this is so).
>
>I haven't been able to find anything in regards to that as well.
>
>>You don't say where this code resides but if this is ASP.NET then is it possible, given the high volumes, that it is a threading issue?
>
>This is VB.NET from a desktop application.

Doesn't neccessarily rule out a threading issue - depends what triggers the call to the method containing the MoveTo (a file watcher for example)

Out of curiosity:
Are you using MoveTo to move the file to a different partition or drive ?
Does this tend to happen with larger files?