Mac Mini dropping internet connection

Hi folks,

I've had a Mac Mini since January 2012.

It's a 2.5ghz with 8gb 1333 DDR.

I have a VirginMedia internet connection using a Belkin Superhub.

Initially, I was running Lion and the Mac worked a treat without any problems. Then I upgraded to Mountain Lion.

Shortly afterwards, I started getting internet drop-off on wifi roughly every hour or so. All access to the internet would cease for around 3-4 minutes - nothing would bring it back. I thought it was a wifi problem, so I purchased two D-Link 500 Powerline adaptors and moved to Ethernet (shutting down wifi). The problem persisted.

The problem does not occur on any other device in the house (I have two iPhone 5, two iPod Touches, a laptop, xBox, iPad and AppleTV). When it happens on the Mac, I can access the internet freely on all the other devices while the Mac sits frozen. I can perform any other activities on the Mac at the time, just not the internet.

The kind of message I was getting in Console referred to mdworker and "heartbeat detected".

I got Virgin out to test my connection, but the line is fine and my setup on the router is fine.

I set a dedicated IP address for the Mac on the router, and set the Mac to use DHCP with a specific IP address.

I set the router to filter the Mac via its Mac address. The problem persisted.

So, with five days of my warranty remaining, I took it to Apple and they tested it - but could not replicated the problem, so they assumed it was an environmental issue and sent me home with my Mac Mini.

As soon as I got home, the problem returned - losing the internet connection roughly once an hour for 3-4 minutes.

So, I reinstalled Mountain Lion. The problem persisted.

So, I wiped the drive and installed a fresh version of Mountain Lion. The problem persisted.

I took it back to Apple and they agreed to look at it again, even though I was now out of warranty. They couldn't replicate the problem.

They put me back to Lion and I took the Mac home. So far so good - the Mac seemed to be working fine.

Then, the problem returned - albeit in a slightly different fashion. I still get the internet freezing roughly every hour or so, but it's now for only about 20 seconds at a time.

When it happens now, I get this kind of message:

26/01/2013 12:30:44.923 com.apple.usbmuxd: _handle_timer heartbeat detected detach for device 0x54-192.168.0.14:0!

I thought it was perhaps Spotlight trying to index an external drive - but I've exluded the drive from being indexed, and it's still happening.

I'm convinced the Mac is faulty, but can't prove it - and Apple keep saying it's environmental.

Does anyone have any idea what might be causing this? I would really appreciate some help.

Best,

CDC