A PostScript error Limitcheck; offending command: String may point to memory related problems. A simple reboot of your RIP may help. If there is a way to provide it with more memory, that might also do the trick.
An application may also write bad PostScript code and exceed the maximum allowable string length. Check if updates are available that address this issue.
Matt send me an e-mail: “I got this error in Distiller 4.0 when distilling a Quark postscript file. I had a duotone that a ‘yellow’ color in it, which I didn’t need so I changed it to a monotone EPS and then the thing distilled. Not proper troubleshooting, but I must move on. Love the site!”