When attempting to print, program freezes...

I work supporting a large healthcare company that has employees in the office and that work from home over VPN. Recently, a network printer they used at the office died and needed to be replaced. The printer was an older model HP that was replaced with a newer model HP. This printer is dedicated to several work From Home employees who need to print documents to the office for the purpose of them being mailed.

We have one end user, who at times can print intermittently. The times when it doesn't want to print, her process is as follows, she opens the document, selects print, the printer dialog box opens for selecting the printer she wants and she selects okay and it freezes. This printer is selected as her default printer.

What has been done so far is,
1. We've tried selecting a local default printer.
2. We've removed the driver and the device and reinstalled it.
3. We've repaired/removed/reinstalled Office.
4. We've rebuilt her profile on her computer.
5. Finally we have attempted replacing her computer as well with a fresh windows 7 image.

After each one of these tasks we've done, it works for a few print jobs, but then returns to doing exactly what is was doing before? We've ruled out everything that comes to mind and what I have researched so far. Can anyone tell me of something we might be missing???

We've checked the VPN and that was ruled out as well. Unfortunately, for them to log onto the network, they have to be on the home internet and logged in via the VPN. Since she is printing to the networked printer at the office, again, she needs to be on VPN. We can't set her up on tethered phone network and allow access to the network.

Since the printer drivers are installed on the print server, we don't install all the other programs that go with the printer. We just install the driver that makes the printer run. She is one of a handful of people who are using this printer from their homes and she is the only one who is having this problem.

The printer is an HP Laser Jet M604

Normally set to spool. We tried both setting and achieved same sad results.

Thanks for useful links. At this point we're trying anything and everything. The poor user has been informed if it can't be fixed she is going to have to return to the office to work instead of working from home as her performance is being affected.