Hi
Using Crystal Reports 2011 you can create read only reports, which will not allow any user to edit it.
File--Report Options--Read Only check box. Just check is it checked.
Also right click on the sub report and go in format subreport--sub report tab and see 'Re-import when opening' is checked. If so, uncheck, save and try in your application.
or
Try to insert a report in a blank report and create a parameter in main report and pass it to sub report and check ur able to do this.
-Sastry