what's the most frustrating linux problem you've had recently?
Mine was a problem concerning my Hauppauge TV card. I had it working under both RedHat and Gentoo, it was perfect, fullscreen, the works.
Anyay, one day i turned on my PC and started xawtv to find a really noisy picture (unwatchable). I tried again, same thing. So i figured it must be the tuning so i ran scantv. It didin't pick up any channels, i double checked the settings and tried again, same result.
By this stage, frustred, i figured it must be the PCI card so i went doen to the shop and bought another card. Took the back off the machine and inserted, rebooted and the picture was still crap.
Rather angry and feeling foolish by now, i recomiled a gentoo kernel - no dice. I took the back off the machine and swapped PCI bays around - no dice. I bought new cables (coaxial) and tried - no dice, i event tried a new jack on the cables. All of this while re-compiling bttv, modprobeing etc etc etc etc etc
By this stage i had spent many hours and quite a few quid trying to fix my TV card. I figured the only thing left to try was the aerial on the roof. I phoned a company to come and check it. When the van was pulling up to my house i could see the driver notice something on my roof. I asked him and he replied that the cable was broken and he could see it from there. 2 minutes later my TV card was running like a dream!
D'Oh! Hours of work and approx $200 later my TV was back.
Now that was frustrating...