There can be a couple of things that can cause this issue; basically this is an issue with Oracle Text / Spatial indexes.
1. Ensure that there is enough tablespace space available for both data and indexes.
2. Ensure that Oracle Text is installed correctly.
If the above are fine, then try dropping and recreating the index on the Problem Summary column. The name of the index is SUMMARY_CTX_INDEX. Ensure that you use scripts that are provided by Oracle to create the index. Run the script cssrcrix.sql and pass the cs schema name(i.e @cssrcrix CS). This creates the SUMMARY_CTX_INDEX Text index.
Please check metalink note Note:312640.1 for more info on building this index.