Document Viewer unable to open DVI files and PDF files not named *.pdf

Hi

Have recently upgraded to Ubuntu 10.04, and I notice 2 problems with Document Viewer:

1. DVI files
Info about Document Viewer says it can open DVI files, but I get:
"Unable to Open Document: DVI document has incorrect format". This DVI file was generated by latex on the same system. Okular opens the file without errors or warnings.

2. PDF files without .pdf extension
PDF files downloaded from arxiv.org have a numerical file number, without .pdf extension. Document Viewer gives the error:
"Unable to Open Document: Error Opening File: Permission Denied." Again, Okular opens this file with no problems. I have checked file permissions, and I am the owner, and Others have permission to read the file.
If I add ".pdf" to the end of the filename, Document Viewer opens it without problem. Ubuntu recognises the file as a pdf, so I don't see why I should need to rename each file before opening.

Can give samples of the files I am trying to open if needed.