I had the same problem. I got the feed URL and downloaded the file. I tried validating it with an online validator and it failed. I then edited the file and noticed that it had carriage return/newline pairs. I removed the returns and it validated and then imported into Google Calendar.
I tried this on another site – same version of A1ec – and it worked fine. I may be running different versions of PHP on the two sites and I do have different plugins, so I suspect a conflict somewhere.
I looked again, and what I notice is that the feed that works has cr/lf pairs, but the feed that doesn’t begins with a lf (0x0a). I suspect that the parser see the initial 0x0a and decides that the rest of the file should use that same pattern. So, something is generating an extra linefeed at the beginning. Time to start deactivating plugins.
Well, that turned out to be easy. One of my plugins had a couple of blank lines at the bottom after the php close tag. I removed them and the calendar feed now works.
