Entering channels manually = wrong channel + I can't change channels after a while

[The Human Co]

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Sound Card: Realtek 880
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1. TV Card: ATI TV Wonder 650
1. TV Card Type: NTSC
1. TV Card Driver: Whatever ATI gave me
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MPEG2 Audio Codec: MPA Decoder Filter
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HTPC Case: Cheap eMachines thing
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Remote: MCE Remote
TV: eMachines 15" LCD monitor
TV - HTPC Connection: VGA

OK, so I'm really, really new to MediaPortal. I read the rules for posting and everything, so hopefully I'm doing this right. Sorry if I'm not. Anyway, I have my TV card set up and all the channels are in, and I'm using the YahooXMLTv thing to import a guide, and the guide works fine - but whenever I try to use the numerical buttons to enter a channel to go to, it goes to the wrong channel. If I enter 6, it'll go to 12. If I enter 12, it goes to 23. If I try 23, it goes somewhere in the 50s. I can't figure out any sort of correlation between what I enter and where it goes, and I don't know how to fix it, either. Also, after about three or four days of leaving the TV going, it'll start doing something where I can't change the channel anymore. The OSD will tell me the description of the show I want to watch, but the video and audio will stay on the old channel. Then, after a little while, it'll just go black and not receive any more channels until I reboot the computer. What should I do?