/opt/alfresco-5.0.d/tomcat/webapps/share/components/documentlibrary/actions.js
correct value:
"
getActionUrls: function dlA_getActionUrls(record, siteId)
…
downloadUrl: $combine(Alfresco.constants.PROXY_URI, contentUrl) + "?a=true",
"
in 5.0.d there was
downloadUrl: $combine(Alfresco.constants.PROXY_URI, contentUrl) + "?a=true" + "\" target=\"_blank",
Problem was with "\" target=\"_blank" which is not recognized correctly by IE
Other lines with ' "\" target=\"_blank" in getActionUrls should be also corrected.
There is also actions-min.js in the same directory, but i'm not sure if it used, so modified locally also.
After changes Edit Offline works fine.