Hi Peri,
If you have access to back end data base then please check one table that is clcFXTrans_Consolidation (clcFXTrans_model name)
All currency conversion rule are stored in the table. Actually there are two tables you can check for currency conversion rule.
1) clcFXtrans_Consolidation(clcFXtrans_model name)--> store currency conversion rule
2) clcFXtransh_Consolidation(clcFXtransh_model name) store rate type
write a query on that table and check,if nothing is their then validate all rule again.
Sushant