Using PBP 2.45 and MPASM 4.01 with WinXP Pro, I can confirm the EEPROM works fine with 18F242, 252, 2420, 2520 and 2620. No blank spaces, odd and even locations accessed.

I have put product out in the field with internal EEPROM maxed-out... if there was any anomaly I assure you it would have been spotted.

I don't have or use Microcode Studio or EPIC.

What 18F is causing you grief? I'll order one in if I don't have it and give it a spin...