Sometimes there are problems with opening attachments in pdf format that contains foreign characters. If there are such problems, a new version of Acrobat Reader should be installed.
There is a bug in old versions V5, V6, so install a new version.
Please go to http://www.adobe.com/cfusion/knowledgebase/index.cfm?id=331025 to get the download link and instructions for installing a newer version of Acrobat Reader.