Hi Barry,
That's great news!

Bits 0 and 1 in the OSCCON register are the System Clock Select Bits. If you look at Figure 3-8 in the datasheet (I link it here just to be sure we're looking at the same revision) you'll see in the upper right hand corner that they, together with the low four bits on CONFIH1H and via the MUX selects which of the various clock sources to use to "drive" the device. When bit 1 of OSCON is set the internal oscillator is selected and bit 0 of OSCON does not matter. You'll see the other options in the overview of the OSCCON register in page 36.

Bit 2 of OSCON (IOFS) is set by the device when the frequency of the internal oscillator block has stabilized, there should, AFAIK be no need for you to write that bit.

Bit 3 of OSCON (OSTS) is set by the device when the start-up timer for the primary oscillator (external x-tal, resonator or RC) has timed out and the oscillator can be considered running and stable. This is also a "read-bit", there should AFAIK be no need for you write this bit.

So, I wonder, didn't my suggested OSCCON=%01110010 work? In your message you say that you've set OSCCON to %0111110 which is only seven bits. I'm not sure if it's the forum messing up the format or if there's a typo?

Finally, you're probably not going to like this but I'm pretty sure that ADCIN doesn't work with the ADC on 18F2431. I know it didn't before and I can't remember seeing any updates regarding that. So, you'll have to resort to manually "running it". I believe Bruce has covered that too in one or more of his excellent posts so its shouldn't be too hard to figure out.

/Henrik.