FYI, there is a new local.currency_code field in the custom.config.php file. It is added automatically but is likely not set right for you. Check for it under the [production] header and for clarity, move it to the other local settings for locale and precision.
Once this is set up, let me know the following:
1) local value settings in the custom.config.php file.
2) What are the settings for currency sign, currency code and locale fields in the INV PREFS (SETTINGS) for Invoice type records.