Right... if someone can work this one out, I'll be incredibly happy (and surprised... but certainly not ungrateful!). 
Problem
I'm experiencing (on 3/4 devices on the network, one wired, two wireless) an intermittent (but frequent) error, whereby the DNS fails to resolve for extended periods. Basically, what this translates to is every 2-3 minutes, a browser (for example) will just sit on "Resolving host...", and then timeout and die (or, if already in the middle of loading a page, will just die mid-page and stop loading anything else, and then time out, leaving broken images, and a partially-loaded page). This lasts for about 40-80 seconds per 'spell'. Obviously, this also affects FTP, etc, etc. - anything requiring DNS lookup.
The router itself, it never loses connection, and the individual machines never lose their connection to the router (i.e. things are still perfectly accessible via their IP addresses... e.g. the router CP).
The one remaining machine in the network seems to work 95% of the time (as opposed to the others, which work only 10% of the time, overall).
This issue started yesterday afternoon, and has, seemingly, got progressively worse over the past 32 hours, or so.
Solutions I've Tried
Booting into safe mode - no effect.
Reinstalling network card drivers - no effect.
Changing browser - no effect.
Performing virus/malware system scan - no results, no effect.
Using a different machine - no effect.
Copying networking settings from a working machine running the same OS - no effect.
Changing DNS provider from OpenDNS to ISP's DNS and back again - no effect.
Resetting the router to factory settings - no effect.
Testing the wired connection for faults - no problems, no effect.
Testing the wireless (an Apple AirPort) for issues - no problems, no effect.
Problem
I'm experiencing (on 3/4 devices on the network, one wired, two wireless) an intermittent (but frequent) error, whereby the DNS fails to resolve for extended periods. Basically, what this translates to is every 2-3 minutes, a browser (for example) will just sit on "Resolving host...", and then timeout and die (or, if already in the middle of loading a page, will just die mid-page and stop loading anything else, and then time out, leaving broken images, and a partially-loaded page). This lasts for about 40-80 seconds per 'spell'. Obviously, this also affects FTP, etc, etc. - anything requiring DNS lookup.
The router itself, it never loses connection, and the individual machines never lose their connection to the router (i.e. things are still perfectly accessible via their IP addresses... e.g. the router CP).
The one remaining machine in the network seems to work 95% of the time (as opposed to the others, which work only 10% of the time, overall).
This issue started yesterday afternoon, and has, seemingly, got progressively worse over the past 32 hours, or so.
Solutions I've Tried
Booting into safe mode - no effect.
Reinstalling network card drivers - no effect.
Changing browser - no effect.
Performing virus/malware system scan - no results, no effect.
Using a different machine - no effect.
Copying networking settings from a working machine running the same OS - no effect.
Changing DNS provider from OpenDNS to ISP's DNS and back again - no effect.
Resetting the router to factory settings - no effect.
Testing the wired connection for faults - no problems, no effect.
Testing the wireless (an Apple AirPort) for issues - no problems, no effect.
