Opening Files in Revit Architecture Suite

[pete]

Often when I open a project I ahve been woking on alone I get the following message:

"This file is already open for editing by another user.  You will be unable to save

  any changes before that user closes the file."

Since I am working on the project alone there are no other users who could have the file open.  So I don't know why I'm getting this messsage.  Any insights?

Thank you,

Peter

[ryan.duell]

Do you have 1 or 2 sessions of Revit open?  If you had the same project open in one, and you opened the project in another session this message would occur.

Could this be the case?

Thank you,