I have the same problem. I have tried to open the printer through the GUI options and it still is not able to open the printer. I have finally found the answer. It is a problem with windows, when you print the PC will stop listening to the printer. You have to take the printer off of the network temporarily and reconnect both print drivers(ups and the pixmapro 100) together. Then when you try to print again it should detect the device and work without issue. This may seem silly but I am very sure there has to be another way but it seems to have worked so far. I would like to thank the person who sent me the fix and helps me find my own solution.
I've already tried the install/repair option and the reinstall option for the TCP/IP drivers, but I still have this problem. I had checked the link that you provided above and I couldn't find anything that explains why this is happening to me.
On my Win XP it took about 2 minutes to install the network drivers and printing, on my Win 7 it takes 20 minutes or more. It doesn't install the drivers, as it says "Classical error: The driver is not installed. Please install the required printer driver first."
Using HP Universal Print drivers for Win XP SP3 and HP Universal Print driver for Windows Vista over both Win 7 and XP Systems it never worked properly. I thought I knew all our troubles -- then I learned that HP's "Universal Print" drivers might not work on other than HP envs. d2c66b5586