I just had this problem. Did some searching and came across this: update.bose.com/soundlinkcolor to update my SoundLink's software. If that doesn't work (or if your unit's software is up to date), do the following:
1. Plug SoundLink's in to wall charger
2. Hold down the play/pause button for 15 seconds.
3. Then, BEFORE releasing the play/pause button, unplug the charge cord from the unit.
4. Release the play/pause button.
5. Plug the unit back into the wall charger.
6. Press the power button, and your unit should power on.
Side note: Steps 1-4 above put the unit in "ship mode" and steps 5-6 take it to 'normal mode'.