The connector on the I/O board has 2 parts - the bottom is soldered to the board, the top snaps to the bottom, sandwiching the ribbon in between. Be very careful when removing the top part of the connector, if the connector won't snap together it won't work, and if the bottom part is broken you'll need to desolder the old one and get a replacement from Bob Roberts. Once you remove the top of the connector, you can pull the ribbon out of the pins on the bottom half. The pins are somewhat V-shaped (similar to a telco punch down block if you've ever seen one of those) and as the wire is pushed into the pin, the edges displace the insulation and make contact with one of the conductors of the ribbon. So you can sometimes fix a flaky ribbon just by giving it a squeeze in the vise and pushing the ribbon back into the pins.