"The specific path is not valid" message

I am getting this message when I try to Write Block a drawing. I can Insert blocks from this same folder, but not save a new block file drawing due to the error message. Any suggestions?

Here is the path to my folder:

C:\Program Files (x86)\AutoCAD 2004\BLOCKS\DETAIL NOTES\new block.dwg

I have not changed any folder parameters that I am aware of, so I am stumped.

AutoCAD LT2015, Win7 Ultimate, 16 G Ram, quad processor.

Also, it deletes the drawing that I am trying to WBLOCK. I am changing the text on a detail block and when I try to save it with the same file name I get the usual choice to save and overwrite the existing file or change to a different file name. If I choose to overwrite the drawing disappears from my screen completely with no pop up notations. If I then go back to Insert and choose that file it does not show the changes. Stumped...haven't had this happen in 10+ years.

Just tried saving the WBLOCK drawing to a completely different file folder and it worked properly. So...the folder path must be corrupted?

Did you check to see if the file your trying to save to is still there plus are you saving on a network? Sometimes when a server gets changed out the ghosting doesn't get all the folders copied. Depends on what kind of software is being used for back up they tend to throw out folders they think are temp folders when in fact they are not. But your workstation doesn't know whether or not if a file path still exists it just tries to save to the last path you gave it. Now what I know about blocks is that even if the original file is deleted the reference for the block still remains in the drawing in which you used it. So you can still use the block in that drawing that it was placed in. But if you try to make changes and the file for the block gone then it wont save because your not changing the block in the drawing your changing the original file. That was what I think is happening but there may be a different reason for this. If your not saving to a network when I don't know what is going on.