Right... sorted it!
Story goes as follows... I originally downgraded it from 3.61 back to 3.55 - started getting BDROM errors with multiman etc.
Here's how I fixed it.
Downgraded from 3.55 KMEAW to 3.55 OFW
Downgraded from 3.55 OFW to modified 3.41 FW
Downgraded from 3.41 to 3.21 OFW
Upgraded from 3.21 OFW to 3.41 OFW
Upgraded from 3.41 OFW to 3.50 OFW (3d Bluray playback)
Upgraded from 3.50 OFW to 3.55 OFW
Then from 3.55 OFW to 3.55 KMEAW again
Installed BDEMUv2 pkg and multiman works fine...
Bit long winded eh?