You probably won't be able to mine with your 4GB Nvidia anymore. There was another individual here that had the same issue. If you are using Windows then try and switch to Linux and "maybe" it will work. Currently AMD cards still work under Linux for me but not Windows.

Another option is that there is another miner called lolminer and it basically allows you to mine past 4GB but with reduced speeds. Basically you can mine a 4.2GB DAG but with a 70% reduced speed. Basically not worth it then but for the first few DAGs past 4GB the speeds aren't that reduced. Maybe they made a version for Nvidia cards and yours should work so try that first. Its on the Mining (altcoins) section of bitcointalk.