PowerPath/VE install on vSphere4

I'm trying to install PowerPathVE 5.4 SP1 to a Vmware vSphere4 host and keep getting the same error. I've downloaded the PowerPath_VE_5.4.SP1_for_VMWARE_vSphere_Install_SW_Bundle.zip to my Virtual Center server (v4) and am using the vSphere CLI to install:

D:\Program Files\VMware\VMware vSphere CLI\bin>vihostupdate.pl --server --install --bundle=d:\PowerPath_VE_5.4.SP1_for_VMWARE_vSphere_Install_SW_Bun
dle.zip

After entering the root credentials I get this error:

Please wait patch installation is in progress ...
Invalid bundle ZIP archive, or missing metadata.zip inside.Bundle /tmp/updatecac
he/PowerPath_VE_5.4.SP1_for_VMWARE_vSphere_Install_SW_Bundle.zip missing metadat
a.zip

I've re-downloaded new bits, cleared the updatecache, tried the 5.4 (not sp1) package. I can use esxupdate on this host for other packages.

Does anyone have any suggestions?

Thanks