AIX: Powerpath upgrade

Hi! I'm trying to upgrade PowerPath from 5.3 SP1 to 5.5 P01.

before:

> powermt version
EMC powermt for PowerPath (c) Version 5.3 SP 1 (build 84)

after:

> powermt version
EMC powermt for PowerPath (c) Version 5.5 P 01 (build 1)

setup:

-boot on SAN plus one datavg

-AIX 6.1 TL06

After reading the doc:

-varyoffvg datavg

-pprootdev off

-reboot

After reboot, only thing up is rootvg datavg is still varyoff.

Unfortunetly, I get this error message when I try to upgrade PowerPath... (smitty update_all)

UNABLE TO UNINSTALL DRIVER: see Installation Guide for instructions
Failure occurred during pre_rm.
Failure occurred during rminstal.0

But if I try a second time right after first failure, it now works...

I've tried this procedure many times with different servers and it's the only way I can make it to work.

Can someone help?