There are many possible things that could be going on here with attempting to match PMS colors on your printer. It is probably not a gamut clipping issue, as the color in question is a neutral. In summary, here is what needs to happen for the Pantone Library in the latest version of Versaworks to be used:
1. Your postscript print file (EPS or PDF) must contain the spot Pantone color.
2. The Versaworks RIP must be configured to look for spot colors in the 'Queue x Configuration'. Edit Menu > Queue A/B Settings > File Format Tab > enable the' Convert Spot Color checkbox.
3. When processing the file, be sure to choose the correct media in the Job Settings dialog. Also, while in this dialog, go to the File Format Tab to check to see if the Spot Color (Pantone) is being picked up in the Spot Colors area (it should be listed).
4. The accuracy of the conversion is based on the ICC profile that is being used.
If this does not produce acceptable results, the other option is to use the Roland Color System instead of Pantone-based colors. This can be done in many design applications, including Illustrator, CorelDraw, and Flexi. This uses a direct conversion to CMYK and can be more repeatable than the Pantone conversion, but is highly dependent on the media.