I had this issue occur with a system on 9.0... we upgraded to the latest 9.1 release and the issue has not recurred.
Note that upgrading from 6.0 will be a multi-step upgrade... You will need to upgrade to 8.0, which will likely also require a RAM upgrade, then migrate data, then upgrade to 9.0 (which rebases the system to Linux), and then upgrade again to 9.1.4.19 (which I believe is current).
This will take SEVERAL hours... with a ton of downtime. I wouldn't recommend this for a regular user, get your vendor involved.