Users without Administer or Browse Project rights unable to assign Issues

Users who should be able to assign the new created Issue, cannot do it - browser displays the "The JIRA server was contacted but has returned an error response. We are unsure of the result of this operation." error.

Steps to reproduce:

• configure the Permission Scheme so that the user has Create Issues and Assign Issues Permissions in the Project (as well as the Browse Users Global Permission);
• create a new Issue;
• in the Assignee field, try to type in the name of a user - error will be displayed (see screenshots from Chrome and Firefox).

Error message in Firebug:

Getting "NetworkError: 404 Not Found - https://instance.atlassian.net/rest/api/latest/user/assignable/multiProjectSearch?username=a&projectKeys=SPTV&maxResults=1000&_=1357731657367"

multiP...1657367