Adobe have some information on PDF-related problems at their site:
According to various sources, this problem can be caused by software/drivers, memory PCA's, font macro personality cartridges, or optional I/O cards. Alternaticely, you may need to replace the formatter PCA.
Try the following:
1. Cycle power.
2. Reset inteface cable
3. Remove Dimms, cycle power
4. Replace Parallel interface
5. Remove EIO cards, perform cold reset
6. Replace formatter.
I trust that this might solve - or at least identify - the problem.