Attachment lost while moving issue

Hello.

I have a some problem with project moving. I have a project with key "ART" (in past this key was "DES") and a project with key "NOKIA". When I moved issue from "NOKIA" to "ART" attachments lost, i see only link to attachment, but link is invalid. In filesystem I see that my attachments moved to "DES" project, but I expected that attachment will be in "ART" project. Also JIRA put new issues attachments to "DES" project and old issues get its attachments from "DES" project too. What reasons for this problem and how I can fix this?

We used JIRA version 6.1(6144)