Open your electrum.dat file in notepad (back it up first), and look for the server name
and port number currently in there (not too far from the top of the file). If you see port 50000, change it to 50001 and save. Now try to run Electrum again.
(This is a known occasional issue that will be fixed in the next release)
how did that arise?
The default server list (in interface.py) has an error for the port number for electrum.bytesized-hosting.com:
DEFAULT_SERVERS = [ 'ecdsa.org:50001:t',
'electrum.novit.ro:50001:t',
'uncle-enzo.info:50001:t',
'electrum.bytesized-hosting.com:50000:t'] # list of default servers
I
discussed it with Tachikoma in August, and he already fixed it in the master branch already. But it hasn't made it into an "official" release yet.