Saw this issue in the readme for v11.52
If this is a legacy project, this may be your resolution.

**Issue User-defined fields:**

When trying to add a custom user defined field in a project that was created originally in Quality Center 9.2 or earlier, a memory protected or corrupted error may occur.

**Workaround:**

Run the following query on the project's schema:

For SQL Server:

UPDATE td.SYSTEM_FIELD
SET SF_ROOT_ID=NULL
WHERE SF_ROOT_ID = 0 AND
SF_COLUMN_NAME <> 'CF_FATHER_ID' AND
SF_COLUMN_NAME <> 'CY_FOLDER_ID'

For Oracle:

UPDATE .SYSTEM_FIELD
SET SF_ROOT_ID=NULL
WHERE SF_ROOT_ID = 0 AND
SF_COLUMN_NAME <> 'CF_FATHER_ID' AND
SF_COLUMN_NAME <> 'CY_FOLDER_ID'