Hmm this is interesting. My room temp is 26C, and the FPGA never reported more than 45C on the 600MHz bitstream.
Are you sure the values are calculated correctly? Whats the temperature without calculating hashes? It should been round about 30-35 °C.
Which temp values do you get from serial port with minicom if no mining is working?
I've modified a little bit the kc705uartworker.py for checking:
print("Temperature: ", "0x" + response, temperature)
Here the results from the console at the beginning of mining. Be aware, the lower values comes from the AVNet MMP
2013-05-24 04:12:54.601721 [500] stdout: ('Temperature: ', '0xA116', 43.97220840454105)
2013-05-24 04:12:55.744079 [500] stdout: ('Temperature: ', '0x9E8C', 38.973677062988315)
2013-05-24 04:12:59.743875 [500] stdout: ('Temperature: ', '0x9FDF', 41.58060340881349)
2013-05-24 04:13:02.601813 [500] stdout: ('Temperature: ', '0xA119', 43.99527854919438)
2013-05-24 04:13:03.744184 [500] stdout: ('Temperature: ', '0xA055', 42.488029098510765)
2013-05-24 04:13:06.601711 [500] stdout: ('Temperature: ', '0xA00A', 41.91127548217776)
2013-05-24 04:13:07.744082 [500] stdout: ('Temperature: ', '0x9F0F', 39.98107337951666)
2013-05-24 04:13:10.601820 [500] stdout: ('Temperature: ', '0x9F85', 40.88849906921388)
2013-05-24 04:13:11.744180 [500] stdout: ('Temperature: ', '0x9E44', 38.41999359130864)
...
2013-05-24 04:22:23.744699 [500] stdout: ('Temperature: ', '0xA77F', 56.59157752990728)
2013-05-24 04:22:27.744679 [500] stdout: ('Temperature: ', '0xA772', 56.49160690307622)
2013-05-24 04:22:30.601187 [500] stdout: ('Temperature: ', '0xB20A', 77.34701766967777)
2013-05-24 04:22:31.744582 [500] stdout: ('Temperature: ', '0xA777', 56.530057144165085)
2013-05-24 04:22:34.601285 [500] stdout: ('Temperature: ', '0xB1F6', 77.1932167053223)
2013-05-24 04:22:35.744667 [500] stdout: ('Temperature: ', '0xA78D', 56.69923820495609)
...