Safari is frozen showing a Shockware Error message windows which reappear continuously. Nothing else in safari works and can't Force Quit or indeed use any other application. Have to force close down machine.

Macbook Pro 10.9.5. Safari has continuous Shockwave Error messages appearing and will not let me do anything else in Safari. Can't access other applications because it won't close or minimise. Only way to do anything is to force shut down of machine then restart. If I open Safari again, nothing has closed and the situation continues requiring another force shut down. Am using Firefox instead but would like to sort this problem out.