Error while indexing my document

Greeting All,

I want to index a file system rep (FSR) that I created in the portal server. This (FSR) has 6520 files. 6492 files were indexed successfully. However, 28 out of 6520 were failed to be indexed:

errored : 28  " Preparation Failed" with multiple Return code

             (14011     "Filter: The file is password protected or encrypted",

              14047     "Filter: Error writing to file",

              14961     "Filter: Access violation", 

              15612     "message not found",

              18096     "message not found")

It is not size issue; some of the indexed files are smaller and some are bigger than the errored files.

it is not permission issue, because some of the indexed files are password protected

and it is not the URL, I checked that and everything seems right; checked the generated URL for some of the error files, and I was able to get into them using that generated URL, especially 6492 files were indexed?

any help, or suggestion on how to fix these errors files.

Thanks