Dropdown value unable to add

Hi All,

i have one custom module, it already has one dropdown field, i need to add few new dropdown value into my existing dropdown field but when i tired to add the value in my dropdown system gives me below error, i'm unable to found that error details in php error log as well as sugarcrm log.

could anybody suggest me how to fix this error. 

my another request anybody please suggest me how i can add dropdown values via code

Any suggestion would be apricated.

Thanks