My old wireless modem/router was starting to struggle under the weight of the wireless devices connected (brought to a head when my son had a sleepover and everyone tried connecting to the wireless causing it to crash horribly).

I settled for Asus DSL-N55U which has been a joy to use....however I've noticed three laptops have issues. They connect to the wireless network fine but I get a little yellow triangle with a ! in the wireless notification and no internet access (or access to anything on the network e.g. 192.168.1.1 or the USB hard drive).

Everything else works fine - i.e. Galaxy S3, S4, 2 x iphone 4s, 1 x ipod touch, 2 x laptops, 3 x desktops (wireless), 1 x desktop (lan cable), Nook, media player, 1 other andriod phone plus probably some other devices I've forgotten about

The three laptops that have problems run XP, 7 and 8.1 (Dell, HP, brand new HP). All three are different beasts (hardware, age, software). Can't even ping anything although ipconfig /all looks all ok

I've tried every setting on the modem, downgraded the firmware, reupgraded it, factory reset it.

On the laptop (well one of them as I figure if I can get one working then I should be able to get the other two to go), I've disabled DNS and manually assigned addresses (slingshot), reenabled it again, disconnected, reconnected, yelled at it (didn't help but felt better from doing it),

The funny thing is if I connect the three laptops using a LAN cable they work fine - no problems whatsoever.

I can't think of anything else to try so I guess I'm in the market for a new ADSL modem/router with wifi, gigabit LAN, and USB for media sharing. I'm a bit wary now as I thought the AAsus DSL-N55U was a fairly good model too (albeit slightly dated).