Wireless works, then stops with SIOCSIFFLAGS: No such device

[infryq]

I'm still a bit of a luser when it comes to linux and gentoo(I did not do this installation myself and am not a hardware person), however I checked the FAQ and past threads and haven't seen anything quite like this.

Firstly: I don't keep the machine as up-to-date as I ought, and the last time I emerged world(a week ago) it left a bunch of unresolved conf files, only some of which I've been able to fix.

Wireless has worked perfectly fine in Gentoo for many months previous to the update. Now, after booting, wireless works fine for a few hours, and then I lose the connection. Attempting to restart eth1 fails, and I get this in /ver/log/everything/current:

dhcpStart: ioctl SIOCSIFFLAGS: No such device

I haven't been able to find anything short of rebooting the machine that can kick the wireless back into gear again(tried: ifconfig eth1 up, dhcpcd eth1, /etc/init.d/net.eth1 restart).

Any ideas? Other problems I found in the forums relating to SIOCSIFFLAGS were thought to be kernel issues, however the fact that mine works part of the time lends me to think that's not the case(how do I find out?). Are there other logs somewhere I should check? Should I just plain not be using the system until all my conf files are resolved?

Puzzled,
Katie