PS CS5.1 will not open my .psd

[rebecca.storer]

So I finished a few hours of editing on the file this morning. Saved it as a .psd and closed everything down. This evening I attempted to open the file and PS tells me:
"There was a problem reading the Layer Data. Read the composite data instead?"

I clicked "read composite data."

PS tells me "Could not complete your request because the file is not compatible with this version of Photoshop."

This is all happening on the same computer, same registered copy of photoshop.

I tried opening it in light room and it says "this file uses an unsupported compression algorithm"

If any one has any ideas, any help will be appreciated.
Thank you.

 

[Paul]

Back up, back up and back up - sorry but it is the only safe way.
Have you tried this http://www.telegraphics.com.au/sw/

 

[Zeealex]

i usually get something similar, only to find i had saved it as a JPEG but added the .psd extension by accident. it would be advisable to backup and reinstall just incase an extension is perhaps missing.

out of interest, what is the EXACT filename of the file?