Sounds like you may have a corrupt file or files. How were the files sent to you? If you recieved a disk perhaps you should have the person suppling the file reburn the disk. Make sure the Mac guy is burning the disk with "You can use this disk on Mac and Windows computers" active.
Have you tried opening the psd files in photoshop? if any or all don't open fine, now you know this is the problem, but if all open fine, you could resave each one and replace the old ones.
You can use a batch action if there are a lot of psd files...
The guy had burned the disk with "You can use this disk on Mac and Windows computers" active apart from that I copied the files to my computer hard disc and tried opening it from there but it still displays the same error messagas. Now the problem is that sometimes the files are opening and can be edited. I even saved the files after editing to my computer, but the error keeps coming even with my saved files too.
Yes the Photoshop files are opening in photoshop I even saved a fresh copy of it but the error still keeps coming regularly. I even tried opening the files in a different PC but it gives the same error messages. I took the files to the PC it was originally created in and it works perfectly in the guy's MAC computer. I tried several times and it never displayed an error message. Whereas 8 out of ten times the file is not opening in any of my client's PC.
Now if the files are corrupt then how cum they are opening sometimes in my client's PC and is always opening in the MAC it was originally created in.