Patch fails with error ” Error occurred in version checking”

Patch fails with error “Error occurred in version checking”.

I was apply patch on the test instance, before applying on the production instance. While apply the patch I found this error “Error occurred in version checking”, I had searched on the internet I couldnt find the solution. My friend told me redowload the patch and try again. I had redownloaded the patch from the metalink. Then I had copied it to the test server through ftp and extracted the Patch. Then i had started patching through adpatch utility. It was completed successfully.

So, What may be the problem. First time I had downloaded the patch archive which was corrupted and some files where missing. Next time, it was ok. So, if the files are missing the adpatch will give this error “Error occurred in version checking”.