Where or how do you get the data displayed on the mashup textbox? For example, is it from an external database? Are you sure database is connected at that moment? Try to search your ApplicationLog.log or ErrorLog.log to see if any error. Usually this may be due to some permission or datasource disconnect issue...
Sometimes it is displaying accurate results. the data is taken from data table.
I checked the Log. It is showing following error.
That error is not related and would be cleared out if you stopped tomcat, then removed these two files:
Then start the tomcat and the files would re-create while clearing the error.
Are you logged in as administrator when the grid issue appears?
What's the user role you used to run the mashup? Is it under the Administrators user group? If not could you try again with another Admin user? If it works properly it's probably permission issue. Then you should grant a proper runtime permission for the user.