You may get the following exception when calling the Update method of the SPListItem class:
Microsoft.SharePoint.SPException was caught
Message="Invalid text value\n\nA text field contains invalid data. Please check the value and try again."
Source="Microsoft.SharePoint"
ErrorCode=-2130575336
StackTrace:
at Microsoft.SharePoint.Library.SPRequest.AddOrUpdateItem(String bstrUrl, String bstrListName, Boolean bAdd, Boolean bSystemUpdate, Boolean bPreserveItemVersion, Boolean bUpdateNoV...
(more)