Unable to use two laptops at same time [Wifi]

[#1]

Hi all, looking for some help.
I set up the whole 'internet thing' today for the two laptops in my flat and it was all going so well. Each laptop (One a mac, the other just a windows operator) seems to work well on both the ethernet cable and wireless.
The problem occurs when both of us use the wireless. My own laptop continues working away fine, but my girlfriend's Mac seems to get nudged off the wifi airwaves. She gets a full 100%/5bar signal, but no connectivity with the little loading logo swirling around aimlessly refusing to load any pages. Obviously this is a bit of a pain considering we are both less than 2ft away from the router.
I have just plugged the Mac directly into the router, with myself using the wireless, and they both appear to be working with no problems. I take the Mac off the cable and attempt to use the wifi, but same problem - no connectivity. Why are we unable to both use the wireless at the same time?
Thanks

[#2]

It can be done, once the problem is sorted.
I run two iMacs wirelessly ( wi-fi ) into my one router at the same time.
I did have a vague logging in problem a while back, when I also had SKY+HD box ethernet cabled into router, once unplugged, problem went away.

[#3]

PlusComUK, so what was the explanation, any idea?

[#4]

No idea, it was the same with 2 different routers.
I don't have SKY subs anymore, so it doesn't arise now.

[#5]

One thing I'd check is the IP addresses of both laptops, make sure that they don't have the same address for some reason (manually assigned?), also can you check the MAC addresses of both and make sure these are not the same (they never should be but... ).

[#6]

we certainly run macs and windows machines (desktops and laptops) on the same network.
Never experienced your issue though, IP address conflict sounds the likely cause.

[#7]

I'm interested in this as I occasionally get "issues" on my wireless network from Apple devices - it's Netgear DGN2000 router at present, though others have had the same problem.
The device, typically an iPhone or iPad just "loses" connection or won't connect at all initially. Sometimes you can reconnect by selecting the network, but often you need to reboot the device and occasionally the router.
As ever, with Apple the information to diagnose it is effectively non-existent.  
Usually through this all the Windows devices work normally, though I have seen the odd "duplicate" IP message so I very much suspect DHCP is at the core of the problem.
I've never bothered to investigate in detail due to the lack of meaningful information or access to change anything in the devices, but it is annoying as the drop-outs always seem to occur at a time when I REALLY NEED that App to work.  

[#8]

HPSauce, the best thing you can do in your situation make sure all your devices are on and working fine on the wireless side, and go into the router page and tell the router keep the same ip address for each device that should solve the random duplicate ip issue.

[#9]

Thanks Taras, I had actually considered that but can't be bothered as the Apple devices are mostly "visitors" of one sort or another. 
My main reason for contributing was to indicate that my "similar-ish" problems seem to be down to DHCP/duplicate-IP and centre round the Apple devices.

[#10]

Hi folks

Quote from: w23

One thing I'd check is the IP addresses of both laptops, make sure that they don't have the same address for some reason (manually assigned?), also can you check the MAC addresses of both and make sure these are not the same (they never should be but... ).

I'm using Plusnet's Technicolor 582n router, is there a way to check the IP adresses and Mac addresses? I logged into the router, but couldn't find anywhere to check these settings/configuration.

[#11]

its http://192.168.1.254/cgi/b/lan/?be=0&l0=4&l1=-1 on the standard 192.168.1.254 gateway settings or
or on the left hand side
Home > Home Network
You should see all devices that have connected to the router past and preset (it can't show future as its no mystic meg! :D).
But seriously though, if you click on the name it will allow you to see the settings and if you select configure at the top right u can then edit those settings
note That link may not work due to different firmware that im on.