Strange little problem, not 100% sure if it's omnibook or linux kernel (ACPI) related. I am suspecting kernel since earlier kernels (2.6.18) didn't seem to do this.
Linux 2.6.29 amd64 on a Satellite U300 (model PSU300C-TP208C)
omnibook driver 280. forced ectype=14 in order to get bluetooth working
1. AC adapter attached, power up (battery indicator is blue or orange, depending on charged/charging)
2. put machine to sleep. once asleep, remove AC adapter
3. wake machine up (resume)
4. plug in AC adapter.
The battery indicator will go orange for about 1-2 seconds, then go out entirely. Battery is not charging, although KDE battery indicator says it is. Battery will eventually drain completely. Unplugging and replugging the adapter will show the battery indicator going orange for 1-2 seconds, but then turning off.
The only way to get the battery to charge again is to put the machine back to sleep, unplug the adapter, wait a few seconds, then plug it back in. when asleep, you will see the battery indicator go orange, and now you can wake/resume the machine and it works fine.
It is as if something is telling the hardware to stop charging the battery.