STB not changing channels?

[Steve52]

I have my my PVR-150 card video source configured to change channels on my STB by using the USB-UIRT. I have an IR transmitter connected to the USB-UIRT, and the transmitter is positioned over the STB IR reciever window. I have programmed the codes for my STB into STV. The IR transmitter seems to be working as it flashes. BUT it will not change channels on the STB. IR codes are being transmitted by STV, but do not change the channel. I have used the test function with STV, and it looks like for every number tested the IR transmitter flashes twice. The IR transmitter (I am not talking about the USB-UIRT which flashes whenever it receives a signal) flashes a light when it receives, and sends I guess a signal. This does not look right to me. I think it should only flash once? I know I am using the correct IR codes I have double checked this. The STB will change channels correctly when using the remote, just not when STV tries. Is there a file I can check to make sure that the IR codes have not been double entered or something? Anyone have any other suggestion as to what could be wrong? The STB is a DirecTv Hughes HTL-HD.