I just completed a recommended system upgrade. It didn't say specifically, but I guessed that it was upgrading me from Oneiric to Precise.

However after the upgrade completed, there were problems. The first thing I noticed was that my netbook no longer had a wireless connection. It wasn't merely that the connection had been dropped; the system no longer recognized that it had wireless capability at all. Only ethernet connections were listed among the network options.

I rebooted, hoping that might restore my wireless, but that only made things worse. After the reboot the system entered memtest, with no option to do otherwise. It ran its tests and reported that the system passed, but then it immediately started running the tests again. And again.

I rebooted again, but was more of the same. There appears to be no way to avoid the memtest or move past it once it completes.

I have some info for you: I just tried to upgrade from 11.10 Ubuntu to 12.04 and also lost my wireless that was working in 11.10. I was told to look at the log in /var/log/jockey and saw my broadcom driver as being blacklisted. So I decided to re-install 11.10 from my disk as simply one way to fix it.
Tom

Thanks Tom. I need to get my system out of memtest so I can boot it, but then I'll give that a try.

If you don't see a boot menu, hit the <Shift> key. Might give you the option to try a real kernel.

Syg, do you mean I should hit Shift during Memtest? There is a brief moment after I turn the system on when I have the chance to change the boot order (whether it boots from the HDD or a USB port), but after that it goes directly to Memtest and I never see another screen after that.

Normally there is a blank screen just after that splash screen that gives you the boot option. I meant in that blank screen period.
Might be worth using a liveCD (on USB is fine) if you have one, or downloading one. Boot that, go here, do as it says, and post the RESULTS.txt. That way we can at least see what is booting.

OK, I tried holding down Shift in that period, and it did indeed get me to a boot screen. Oddly enough the graphics in the boot screen were for Debian rather than Ubuntu; I guess no one has gotten around to changing that since the fork.

In any case the boot screen offered a list of operating systems to boot into. However the only options listed were two different versions of memtest. Ubuntu wasn't listed at all, which I suppose could explain why the system couldn't boot into it.

At that point I decided to stop fooling around (the machine has been idle for many days now). I booted from a live USB and offloaded any really critical files, then I simply re-installed from the live USB. Fortunately I had planned ahead when I did the first install on this machine: I created separate / and /home partitions, with all my data on /home. So I re-installed on the root partition and when I brought it back up all of my data was still intact.

I'd been hoping for a more elegant solution, not only for myself but for anyone else who has this problem in the future but doesn't have a separate root partition. However the brute force approach worked fine in my case. So I'll mark this one SOLVED even though it wasn't pretty.