I've searched now for "chrome empty images" and found that this "problem" with empty images isn't unknown. (Seems that there can be troubles with chaching images when often reloading the same page/image/.. )
[Edit]After a few tests I have the following:
for Chrome 18.0.1025.142 m (+19.0.1084.9 dev-m):
-) WebGL - only Sprite saving works - having the same issue as above
-) canvas2d - all actions work
Firefox 11.0:
-) WebGL - all actions work
-) canvas2d - all actions work
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I'll try to update the plugin for the chrome WebGL-renderer - asap.