TV Options... > General > Load Program Guide... to bring up the "Load Program Guide" wizard.
On the first page of the wizard, your choices should already have been selected if you previously have run this wizard, otherwise choose your country, postal code, and most importantly, your cable provider. Click Next.
On the next page, you should have a list of your channels. Next to each channel is the name of xmltv ID (or "(Click here to configure)" if the channel is not associated with any ID). To add or edit an association, simply click the channel entry. You will get a list of all xmltv ID names, which may or may not be identical to your channel names. Find the right one to associate with the selected channel. Also you should remove the association with your old channel (if the old channel is still in the list). To remove an association, click the entry and select the blank space at the top of the drop-down list. Click Next after all channels are correctly associated.
Click Finish.