OS10.6 & OS10.7 (MM) won't mount BD, but OS10.5.8 (G4) will?

What I have: (the problem is explained below):

Model Name: Mac mini

Model Identifier: Macmini4,1

Processor Name: Intel Core 2 Duo

Processor Speed: 2.4 GHz

Number Of Processors: 1

Total Number Of Cores: 2

L2 Cache: 3 MB

Memory: 8 GB

Bus Speed: 1.07 GHz

Boot ROM Version: MM41.0042.B00

SMC Version (system): 1.65f2

Serial Number (system): < Edited by Host >

Hardware UUID: A8EBDDAE-BD8B-5AC7-8235-3AD66BF0EB5E

MATSHITA BD-MLT UJ240AS: (EXTERNAL USB connection)

Firmware Revision: 1.01

Interconnect: USB

Burn Support: Yes (Generic Drive Support)

Profile Path: None

Cache: 2048 KB

Reads DVD: Yes

CD-Write: -R, -RW

DVD-Write: -R, -R DL, -RAM, -RW, +R, +R DL, +RW

BD-Write: -R, -RE

Write Strategies: CD-TAO, CD-SAO, CD-Raw, DVD-DAO

Media: To show the available burn speeds, insert a disc and choose View > Refresh

OS: Either OS10.7 or OS 10.6.8, I can boot up in either.

The MATSHITA BD-MLT UJ240AS is connected via USB from which it gets it's power. Due to the limited USB ports on the Mac MIni have a USB HUB which I use to connect the MATSHITA.

I purchased the MATSHITA BD-MLT UJ240AS under 30 days ago, and it's taken me that long to get some blank BD-RE media to test it.

Problem:

When running EITHER OS10.7 or OS10.6.8 on the Mac Mini: (I can boot into either):

- The MATSHITA BD-MLT UJ240AS is recognised by the system, however if I load a BLANK BD-RE or BD-R the system will attempt to read them for a short period of time then spit them out. They do not mount.

- If I load a BD-RE will data burnt on it the system reads it for a short period then spits it out. It will not mount it.

- If I load a Region FREE commercial BD disc the system will recognise and mount it.

- If I load a Region LOCKED commercial BD disc the system reads it for a short period of time, then spits it out. It will not mount it.

However:

When I connect the MATSHITA BD-MLT UJ240AS to my ancient PowerMac G4 running OS10.5.8:

- The MATSHITA BD-MLT UJ240AS is recognised by the system, and will mount BLANK BD-RE and BD-R disc's. A message pops up and asks me what I would like to do with them.

- If I load a Region FREE commercial BD disc the system will recognise and mount it.

- If I load a Region LOCKED commercial BD disc the system will recognise and mount it.

I am at a loss to understand why the MATSHITA BD-MLT UJ240AS works so well on my old G4, and not on my year old (Intel) Mac Mini.

Is this an OS issue?

Is this a hardware ie: Mac Mini, issue?

Does anyone know what's going on and /or have a solution?

Happy to receive any thoughts or suggestions.

Thanks.

Robert.