Warning message- Already opened document

I am have been having a warning message when I have been trying to open drawings the past few days.  It is saying that I have an already opened document, would I like to show this as an already opened document. 

I have nothing else opened in solidworks so I am not sure what is going on.

Any help would be much appreciated.

Thanks,

Colleen

SolidworksDrawings And Detailing