Hi Patrick, I can not upgrade base module which Keyur mentioned because my database has some purchase order....records. And I can not manually create a currency (with currency rate) because the original ones are all gone, it is blank there, and i can not create with the warning(screenshot showed in my question) as well.

It worked for me. After disable the "base" checkbox I could add custom period

Yes? You means upgrade the version to the latest one(I am using version 7.0-20130327-002325 right now)? Because I tried to create one currency(assume it was deleted itself) and system said you can not do that because unique code reason. so i think it implies the currencies should still there in system but somewhere I do not know.

Here I've got the same problem when I create new currency record. Current rate is already set to 0 and readonly field so we can't create our currency that way. The problem is solved by discarding the changes or reloading the page. Even if there are any issues then try to upgrade base module in settings->Modules->Installed Modules->Base.

Thanks but I can not update the base module. the screen shot of warning notes is as above in my question.

Hi Dharmesh. I think there are some restrictions in version 7.0, currency record can't be created directly from web client. The Current Rate field in currency form view is set to '0' by default and it is readonly. So is it the proper way to change directly in database every time we get error like this?

There is no restriction in OE 7 and rate fields be always editable otherwise it will never possible to update new rate for currencies.

Hi Dharmesh, I did set up currency rate before, and the amount can be calculated by the rate i set. The situation now is I lost my old currency records(with their own currency rates) entirely, and now i can not upgrade base module and create currency.