That thread you linked to relates to a Linux installation but if you look on Intels list of supported OS's, your board (along with almost all other recent boards on the list) is not listed as having support for Linux. What OS are you using and what company is the manufacturer of the Serial Adapter board? I know you're probably keen to use one of your 3 PCI slots but as a simpler workaround, have you considered a USB to serial adapter?