Hi
I've been hitting the same issue using update manager using the v5.5u1 HP Customised ISO. The method below seems to workaround the issue.
With 5.5 installed, manually INSTALL (not UPDATE, as this fails due to a dependancy) the lastest Broadcom drivers using cli etc.
# esxcli software vib install --depot=/tmp/BCM-NetXtremeII-4.0-offline_bundle-1796156.zip
Once rebooted, try the upgrade to 5.5u1 again. You shouldn't see the validation errors like those described in the original post.
Hope this helps somebody out.