Looking at the code, i remember the actual problem here. It's this: Before creating the AWTGLCanvas, you can't query the driver for features because you have no context. The context itself is created inside of the canvas' paint method by LWJGL. If the hardware doesn't support the sampling mode, this fails and the canvas calls a method named exceptionOccured, which is the method that prints out the error message you are seeing.
The problem is, that you actually can't change the pixel format afterwards. It's feeded into the constructor of the canvas and goes into a private field. So you end up with a canvas that can't initialize itself properly (but tries again in each iteration...), you are aware of this...but you can't change anything.
I've uploaded a new jpct.jar here:
http://www.jpct.net/download/beta/jpct.jar. In case of this error, it tries to inject a new pixel format into the canvas via reflection, modifies some other fields of the canvas so that it thinks that it's new and makes the canvas reinit itself this way with a proper pixel format in the next paint-call. This is very hacky...and it only works as long as the behaviour of the canvas doesn't change.
Anyway, just give it a try and tell me if it helps.