What version? We are successfully pushing out V5R4M0 with no issues.
We use Wise to package the upgrade the V5R1 Client Access Express to V5R3 iSeries Access for Windows and then to V6R1 System i Access for Windows. The process actually works great, IBM did a good job to my surprise. A reboot prior to upgrading is a MUST.
That would be the one.
How are you pushing it out?