Ken, this is another Ken here from Johannesburg South Africa.
Your problem is not unique. Others who have had the problem have found that enabling multicurrency and selecting GBP as their home currency resolves the problem (for no known reason; QB simply has a bug in this respect). QB UK tech support now apparently recommends this as the standard remedy. You might like to try it. Of course, once you have enabled multicurrency it is irreversible but I had to do so for similar but not identical reasons and it has not caused any problems.
UK tech support did concede that there is a problem in the 2005 Regular version and gave a user a free upgarde to the Pro version. Perhaps you can get a free upgrade to the Premier version!
I take it that you have checked in MS Windows that currency is set to GBP (Start + Settings + Control Panel + Regional and Language Options).
If you still have a problem after trying these suggestions I have a lot of further suggestions you can try.
Ken