It is not &nocache=1 but &nogadgetcache=1 that must be added;
make sure you append this before the # in the URL !
from the docs :
Changes to gadget don't show up immediately.
Gmail is probably using a cached version of the gadget. Changes to gadgets can take some time to be reflected because of caching. Solution: Make sure you include the flag &nogadgetcache=1 in the URL when you start Gmail to test your gadgets. This flag ensures that any changes you make to gadgets will show up in your Gmail account immediately. If you reference external resources in your gadget, such as JS or CSS files located on external servers, those resources are still subject to caching.