OK, so then it's some kind of interference between the SPWM routines and the rest of the program, perhaps a read-modify-write issue, I don't know. But then you say that you had a version with both SPWM and I2C on the same port (different pins of course) which DID work so I don't know. Hopefully Darrel or someone else who's been using the routines in quesiton will jump in.

Back to the hardware PWM.... Did you set the registers manually or did you use the HPWM command?
If you set the registers manually then the number of bits of resolution you get depends on the frequency you select so a dutycycle value of 255 doesn't neccesarily mean 100% - it depends.
If, on the other hand, you DID use the HPWM command then you should have got 100% with a duty of 255 - given you had told the compiler the correct operating frequency, ie DEFINE OSC xx.

I still think you should concentrate on getting the CCP modules to do the PWM for you. Post the code for that and I'll take a look.

/Henrik.