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Sorry I haven't replied earlier, been busy, I have contacted tech support at the hosting company, they have logged into the site and witnessed the problem occuring. The first level tech briefly mentioned he can see that there may be a "session problem" after he viewed the logs.
He is going to escalate it to the senior techs, we will see what they have to say. I will update this thread when I hear back from them.
Thanks for your help ghia!
Cheers ;o)