HP-6040, we are intermittently getting “Failed to print” error.

When printing to HP-6040, we are intermittently getting "Failed to print" error. This is happening for all staff and there appears to be no obvious pattern as to which jobs print and which jobs fail to print. For example, this morning I successfully printed an MSWord document, then a PowerPoint document, but when subsequently printing another MSWord document it "Failed to print".
