A:SY:002 Invalid call to a database interface (SAP)

[tomuri]

I have open SAPMMC
SAP R/3
START 3.O
PROCESS LIST (all showing green)

WP TABLE

all status are showing wait.

When I logon to SAPLogon 620, click new,
Type in all the entires.
Description.Application server, system number (00),SAP system r/3.

then OK.
the following error is displayed:
A:SY:002 Invalid call to a database interface

can anyone help....many thanks