Please make sure that you installed the lpr and cupswrapper then try this below, it should fix it.
Ubuntu 8.04 does not have /usr/share/cups/model directory where our driver create a ppd file.
Please follow the instruction below when the installation failed with the message about it.
1. Uninstall the cupswrapper driver.
Command : sudo dpkg -P (driver name)
2. Create /usr/share/cups/model directory
Command : sudo mkdir /usr/share/cups/model
3. Install the cupswrapper driver
Command : sudo dpkg -i --force-all --force-architecture (driver file name)
Let me know if it helps!