SAS isn't so good at resolving external errors. Could be lack of disk space, could be network connectivity glitches.
I've found in the past that if this keeps happening, it's worth working on your local disk, then copying the data across using file system tools (ie doing it through your OS or a script or something). If it's something that is done regularly and you want it automated through SAS, you can use the X command to access OS command line commands.
Chris
Business Analyst, Code Monkey, Data Wrangler.
SAS Guru.