I tested the two last version of your plugin several time.
I tested you plugin on a cleaner wordpress version also with weaver and on the same hosting service and it works.
So the problem is probably coming from another crazy widget conflicting with yours, here is the list I use:
-sidebar login (using ajax)
-weaver text 2 (should be alright
-recent forum post (from simple press forum) (perhaps also this one)
Here we are.
If you have a special test, that you want I do, I'm open. but I don't have the time and skills to test allll the different solutions right now...
Thank you for your fast replies. And if you want to test some stuff, then just tell me.