You may have noticed that when you have a new installation of reports 11.1.2.0 when you try to run a PDF report or even if you simply try to do a showjobs request you get the error REP-52262 Diagnostic output is disabled. It seems that in a new installation for security reasons diagnostic output from the URL is disabled by default.
If get this pesky error it is actually quite easy to resolve using these easy steps:
1) Backup the rwservlet.properties file located in %DOMAIN_HOME%\config\fmwconfig\servers\WLS_REPORTS\applications\reports_11.1.2\configuration
For example:
C:\Oracle\Middleware\user_projects\domains\FRMDomain\config\fmwconfig\servers\WLS_REPORTS\
applications\reports_11.1.2\configuration
2) Then edit the rwservlet.properties the file in notepad++
3) Search for the the lines
<!–webcommandaccess>L1</webcommandaccess–>
4) Remove them from comment so they will look like this
<webcommandaccess>L1</webcommandaccess>
5) Then change the value from L1 to L2
So it will look like this
<webcommandaccess>L2</webcommandaccess>
6) Save the file
7) Now all that’s left to do is to restart the WLS_REPORTS domain
This can be done either via:
1) The weblogic EM console
2) The stop and startup scripts in program files of the server machine
After the WLS_REPORTS is restarted you will see it working!
A shout out to PITSS for helping resolve the issue.
Oracle Developer Community 
We have just found that the REP-52262 message also starts appearing after patching 11gR1 from 11.1.1.6.0 to 11.1.1.7.0, and is also easily resolved by making the same change to the rwservlet.properties file.
Thanks for the tip!
In OAS 10g it will be in differenct place at miter home $ORACLEHOME//reports/conf
Have to disable the statement #DIAGNOSTIC=No, then try to restart the perticular report server. It works