I have no experience with this  thing, but here is a link for 
troubleshooting some problems on the 4500.   I also  see the reset 
procedure is shown here, maybe a reset will help.

http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=c01952299&lang=en&cc=us&contentType=SupportFAQ&prodSeriesId=3919445&prodTypeId=18972

73, Steve KW3A
On 2/19/2013 10:18 AM, Walt Sebastian wrote:
> Hi Guys,
> As the subject line says, I am enquiring about the HP printer.  It is in =
> a strange mode, or something.  It will not fax or       copy.  It says =
> =E2=80=9Credial in 0=E2=80=9D and when the green button is pressed, it =
> says busy.  How     can I fix the problem?  Thanks.
>
> Walt
> WA4QXT
> Groton CT
> [log in to unmask]
>
>
>