'unsupported blending mode' among other errors

Hey folks

I recently had to make the move from CS4 on Mac OS 10.5.6 to CS4 x64 on Vista.

I opened a file and worked on it with no problems on the new CS4 x64 setup. It also saved multiple times throughout with no apparent problems.

When I have tried to reopen the file on the same CS4 x64 Vista setup I get the following errors in this order:

--

This document contains unknown data which will be discarded to keep layers editable. To preserve the original appearance instead, choose Flatten to load composite data as a flattened image.

Options - Keep Layers, Cancel, Flatten

(If I choose Flatten I get this error: Could not complete your request because an unexpected end-of-file was encountered)

I choose Keep Layers -->

--

The file uses an unsupported blending mode. Substitute normal mode?

Options - OK, Cancel, Flatten

(If I choose Flatten: Could not complete your request because an unexpected end-of-file was encountered)

I choose OK -->

--

A problem was encountered reading layer

"Shape 1 copy 220"

because of a program error.

Continue?

I choose OK -->

--

Some groupes were found corrupted and repaired.

OK -->

--

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

OK -->

And the file has closed itself.

I cannot open this file on either CS4 on the mac or CS4 x64 on the PC.

As a side note, this particular file is a personal blog design I've been working with on and off for several months so I can't be 100% sure, but I don't believe I have a layer called 'Shape 1 copy 220' as I surely would remember copying a layer 220 times.

Of course, it is annoying that I lost maybe 4 hours work (I have a backup of the original file), but my main concern is this happening again - especially with commercial work. Can anyone shed any light on known issues between Mac and PC versions of CS4? Is there anything I can do to prevent this from happening?

Any help greatly appreciated.

Dave

I'm not 100% sure, but it seems a file corruption issue. The original file works?