I copy/pasted an address from a page, and it included the character U+2028 (LINE SEPARATOR) at the end. When I clicked Send, it did nothing visible and logged this:
2015-04-07 20:19 (ERROR) -- Traceback (most recent call last):
File "ui\TxFrames.pyc", line 758, in createTxAndBroadcast
File "ui\TxFrames.pyc", line 429, in validateInputsGetUSTX
UnicodeEncodeError: 'ascii' codec can't encode character u'\u2028' in position 33: ordinal not in range(128)
Being a whitespace character, and having no visible error message, it wasn't easy to realize that I had an extra character at the end. I would expect it either to work or to tell me there's a problem with the address.