the only reason i can think of that could cause the second drop down list (Source) to have a smaller number of selectable items is when you set the first drop down item (Fiat currency) to another currency.
so make sure that your "Fiat currency" is set to USD first and see if that fixes the issue.
I'm in europe so i use EUR :-D,
i've fix the problem, i copy the config file (in .electrum folder) form the "new" electrum and replace it in the "old" electrum, now i see correctly 11 exchanges (in euro).
Pindol