Network or Printer Problem

Did you try deleting and re-Adding in Print & Fax?

Even better than that, if it's your only printer, reset the printing system. Hold down option when you click the minus button to delete the printer. It'll reset print queues, delete pending jobs, and remove the printer.

If it works via USB and doesn't work via network, but you can see it, it's likely to be a network issue. I actually had my Canon printer do that yesterday. It got halfway through printing a page and stopped. Eventually it spit out a half-printed page. I rebooted my airport and retried and it printed. My network is a mess, so I didn't think anything of it.

Reset both your Express and T.C. (power off 10 secs, then back on).
The Express is set to use bridge mode (Distribute IP addresses is off?)?

A test page is typically pretty small.

I've seen driver issues cause similar problems, but you said you've just updated the drivers. You've got a pretty common printer, so I doubt the driver is to blame.

I saw a Ricoh printer recently for which reliable Mac drivers did not exist, we had to set it up with an open source driver. It printed test pages fine, but any time I went to print from Safari, Word, etc., it sat and spooled for EVER. It was a networked printer, something to do with the driver rasterizing and generating huge files that then took forever to move across their 10/100 network.

When you print from an application, watch the print queue as it sends the job. Does it seem to be sending right away? Does it sit and try to send for a very long time? Does the printer sit at "Printing from PC" or something similar for a long time?