I have a PIC to PC and PC to PIC circuit operating just fine. However, when the circuit is moved to different PC's, I have noticed the data coming from the PC is not always detected by the PIC. It appears the voltage level from the IO port on the PC is lower. I have placed a MAX3180 on the receiving side of the PIC to boost the voltage. And it does. The MAX3180 inverts the data. I have been using N2400 and 16780 as buad rate perimeters on both sides of the PIC, Xmit and receive, and things had been running quite well. I changed the receiving side of the PIC to 396 but haven't had any luck making the connection. Is there another value or trick to this? This is the first time I have had to use a line driver with a PIC.
The basic PIC data circuit is layed out like the manual suggests, nothing else.
Thanks in advance.

Brad