Kontact "locked" problem

[Brian Astill]

I've been running Kontact successfully for several months.
Everything - including looking up existing records in Contacts - seems to work 
just fine.
However, recently the Contacts section has prevented me from making any 
changes, and comes up with this error message:

The resource '/home/bra/.kde/share/apps/kabc/std.vcf' is locked by application 
''.

Of course, I do not have an application called ''   :-)
Clues how I might correct this problem, anyone?

-- 
Regards,
Brian