I'd take a look and the assembly listings machine code and confirm that the equates for the port.bit is correct.

The assembly listings reveal all. You may find that a STRING you are using for the port.bit is actually used as a register name.

It should be something obvious but overlooked like that since you've confirmed the pin input with the oscilloscope. When reality appears violated, it almost always means one of your assumptions is wrong. Challenge your assumptions; make sure the code is inputing the pin you expect and that it is initializing the input pin high. Check the machine code in the assembly listing and look it up to make sure.

Post some code.

If you have a spare I/O pin you can use as an input, wirewrap to that pin (don't cut the trace). If it works there, you'll at least confirm a peice of reality. :)

aka j