Have noticed some errors in build 1338, both US English and Spanish in Windows and Mac platform.

When the desktop tries to open a popup, you get a nasty box.

See
Can not download attachments - Vista Business x64

Another examples where you get the error are:
- The confirmation box when deleting an account.
- The confirmation box when stopping service (seen in Windows Vista).
- When opening an attachment (applies also to Mac version, the workaround is the same as the referenced post).