Trouble shoot tips for Error code 156(Snapshot error)

you can find the lot of T/N in the google about this...thouch 156 is the same status code the reason might be different for each case... you need to deal with it case by case.. rather than looking into the generic docs..

i would suggest you to start from below.. 

http://www.symantec.com/business/support/index?page=content&id=TECH47808

lot more in google...

I agree with Nagalla. Google is your friend.

Another TN I have found:

VMware status 156:
http://www.symantec.com/docs/HOWTO44492

It helps to add the error message before you see status 156 and detail such as the OS version and backup type.