Unsupported format or damaged file

Are there naming conventions or bugs that might limit import into Premiere? We recently experienced that files in four specific folders on our Nexis central storage wouldn´t import, giving the error "Unsupported format or damaged file". Copying the files to local computers would let us import the files (same file name, but obiously shorter string). Also, renaming the files on the Nexis (just putting a "1" in front of the file name) would enable import. So at least the string is not too long. Would appreciate if anyone has input here, as the production in question is quite large and we name our files a certain way to keep file and folder structure throughout the whole editing and post production process.