m i wrong???

hello everybody...here is my schematic diagram for my infrared encoder mcp2120.now the problem is everytime when this system being started it will work properly for around 5 sec...after that the signal wil getting lower and lower until no signal finanly.could it coz my capasitor prob???

remarks: baud0:band2 set to 0 for 9600 data rate.using hardware selection mode.

I suspect that if you carefully trace the circuit, you will find that it is not wired like the schematic.