events not working with eip 55 Mixed-case checksum encoded address

[nkraetzschmar]

When instantiating an existing contract using

contract.at(callback, address);

(where address is encoded as an eip 55 Mixed-case checksum encoded address)
listening to events doesn't work:

contractInstance.someEvent({}).watch(eventCallback);

No exception / warning is being raised, however the eventCallback function will not be called when the event occurs.
Getting old events works without any issues no matter the address encoding.

The obvious workaround is using

contract.at(callback, address.toLowerCase());

but it would be nice if checksum addresses worked as well since they work without problem for anything else.

[tmashuang]

Consolidating to #2393