I have been using Open2300 1.10 with Mandrake 10 with no problems. I recently reloaded the same hardware to CentOS 5 (stock kernel version 2.6.18-8.1.8.el5xen).
I compiled new copies of Open2300 and used the same config file (ttyS0 does seem to be correct in both distributions).
However, any of the programs such as fetch2300 hang for a long time and eventually fails with the message "Could not reset". It appears that temperature_indoor() is hanging on the statement:
if (read_safe(ws2300, address, bytes, data, command) = bytes)
I have tried the Non Blocking Open patch on 1.10 but it did not fix it. I have also tried 1.11 and it hangs as well.
Update: After much digging, I found the answer. It appears the Xen console grabbded /dev/ttyS0.