It might be that your hosts standard setup is something other than 755. Ask your host what the standard folder/directory permission level is for the server. If they tell you 750 or 705, etc. then you would want to go with that instead. There are a few hosts out there that have some pretty tight less than standard setups. Not that it is bad, just scripts like dolphin quote the more standard, and occasionally you get a host that uses a different setup.

I also had this issue with previous RCs and found it was actually my FTP client that was the problem. I worked around it by changing the permissions via the Cpanel instead.