New Line - when both lines are in use both the lines lose connection.

[#1]

Yesterday I had a second broadband line installed at my property.  I was advised that in order to get the second line a a pair divert was used.
Now when both of my internet connections are uploading and downloading they both simultaneously disconnect from the internet.  Some connections remain but some disconnect.  The lines are used heavily.  Individually though they do not disconnect.  It is only when both lines are being used at the same time.
Could it be that this pair divert was placed on my existing line and is now causing an issue when both lines are in use?
The only reason to have a second line was to increase the speeds of uploading and downloading things for my business and to also have a backup should one be running slower or struggling. 
Would these disconnects show up to plusnet bearing in mind that only certain things disconnect but some otehrs remain.  It varies each time.

[#2]

Hi kazagamez,
Thanks for posting. Just so I can get an understanding of how your internal setup is in the first instance, can you please give a brief description/summary of your internal setup?
Is everything connected via Ethernet? Before looking at the potential that an external influence is causing the problem, it is possible that something internal could cause this which we'd be best looking at first.

[#3]

Hi Chris.  Everything is connected through Ethernet separately.  The Plusnet is supplying 1 PC and the Sky lines are supplying separate PC's also via Ethernet.

[#4]

So, internally, there's nothing that could be causing the disconnections?
If this is the case, I would strongly suggest raising a fault at http://faults.plus.net

[#5]

I have tried that Chris.  They run a test on the line and tell me everything is ok.  The issue is not that I lose internet connection altogether.  The issue is that I am unable to connect to any new servers.  Online games/web pages/ skype etc.  Anything already connected remains connected.
Again this is intermittent and only occurs when both lines are being used heavily.
There is no interference between teh 2 lines modems computers or anything else for that matter.