Strainge networking issue with multiple LAN's

"Hi community.
Like the look of the new site dev guys.... will take me some getting used to though! As I might have all ready posted this somewhere in the forum's all ready. Sorry if i have but its a no show if I click "show my posts" option. "

I have a ClearOS gateway with multiple NIC's set-up for multiple LAN's. I have provided a brief description of the layout below.

ClearOS Gateway
LAN1 in LAN mode
192.168.15.1
255.255.255.0

I use LAN1 for the local network, no restrictions just a simple LAN for all my home devices.

LAN2 in LAN mode
10.15.0.1
255.255.255.240

Will become a DMS once I switch ISP in September. For now I will more than likely change to HOTLAN mode at a later date, as will be used for internet facing services E.g game servers

I have an ubuntu 14 server also with multiple NIC's and this is where the problem starts

NIC1 connected to LAN1
Static config
192.168.15.254
255.255.255.0

NIC2 connected to LAN2
Static config
10.15.0.2
255.255.255.240

Now onto the problem.

If I have just one NIC configured say NIC2 I am able to ping it using my windows machine connected to LAN1 and am able to access the services on it say game servers.
If I then enable both NIC's in the ubuntu server I can no longer ping NIC2 but I can ping NIC1.

When I connect my laptop to LAN2 the same is ture for that network. I can ping NIC2 but not NIC1, and If just NIC1 is connected I can ping NIC1.

I then connected my laptop to both networks and this showed the same result.
Windows machine could only ping the laptops conection to LAN1 and the ubuntu machine which at this time only had NIC2 configured could only ping the laptop on its LAN2 connection.

When both NIC's are configured on the ubuntu server I can no longer access its services via LAN2, however they are still available to the internet and systems connected to LAN2 only.

I think this might be a routing issue and have found lots of info regarding setting routes too and from certain networks, and default NIC's for said network traffic. Of witch I have tried many and none have made any change to the behaviour of he network.

So far these routes have only been applied to the ubuntu server machine but I'm not sure that’s where the problem is.

If any one cloud point me in the right direction, or shed some light on this I'd be grateful l.