There are some lessons to be learned here.
Several guys have been scratching their heads, all coming up with quite possible solutions to the problem as it was originally presented - a problem with a 78L05 regulator.
When the big picture is on view (the PIC with an input pin connected to the input of the regulator), the problem becomes obvious.
Lesson 1, describe the whole problem, not just the little bit which APPEARS to be causing the fault.
The OP eventually gained insight into (but not the reason for) the problem on his own, by disconnecting the rest of the circuit from the regulator. Well done.
Lesson 2, when nothing makes sense, break the problem down into little bits, find out what works on its own, then start connecting the bits together one at a time until it stops working. Then you have most likely found the problem.
JimB