Great, I'm glad that it works!
I can't say I understand WHY though.... Setting the lower two bits of OSCCON to 00 selects the primary oscillator as the source while setting it to 10 selects the INTOSC, I thought the PIC should be run by the internal oscillator.... Oh, wait, NOW I think I see what's going on...

Look at the figure 2.8 in the datasheet. When we select INTOSC by setting the lower two bits in OSCCON to 10 we're driving the chip directly from the internal oscillator with whatever frequency we set it to. The signal comming out of the "OSCCON MUX" in the diagram is selected to drive the PIC via "Clock Control MUX".

But when we enable the PLL we have the switch the clock source from INTOSC to the Main Oscillator block (even though that's what we use with EXTERNAL crystal) so that we get the signal from the PLL (which is now driven by the internal oscillator). The "real" primary oscillator is disabled though because we've selected the INTIO67 mode via the CONFIG bits.

Anyway, I'm glad you figured it out, good luck with the rest of the project!

/Henrik.