We are get the same error as JRA-4936 under 3.0.2 Professional:
After setting up JIRA on Tomcat5, we go to the URL:
Http://localhost:8080/jira
This redirects us to the setup screen. After filling the information fields, including our license, clicking Next yields the following message:

"Could not activate indexing: Cannot activate indexing as it is already active."

The path is set to "C:\atlassian\atlassian-jira-professional-3.0.2\indexes", and the folder is created successfully. We appear to have the newest professional version (#72). Was the fix in JRA-4936 applied in this version besides Standard?