18f4550 running slow?

[J. Mark Wolf]

I experienced something similar to what you describe awhile back.

In my case, the OSCin and OSCout pins were not configured properly in the Config fuses, so the ceramic resonator was failing to run reliably, and it was defaulting to the internal oscillator, which was running at something much slower(possibly 32Khz). This is controlled by the IESO fuse, Int/Ext Oscillator Switch (at least on the 18F2620).

Check your fuses.