Opening a page from Composer (either through File->Open or the Open toolbar button) brings up a file open dialog, but when you select the file, it doesn't actually get opened. Using File->Edit Page from the browser works fine.
apparently this doesn't work in the browser either...
assigning to sfraser for debug
This works for me on Mac. Is it really linux only?
I can open files in composer using my linux build from today. Do you have a sample file where this doesn't work? Maybe it's a problem with the specific file? What sort of console output do you see after hitting ok on the file selection dialog?
I tried with two different files, one of which was just a skeletal HTML file, so I don't think that's the problem. I'm doing a build right now, I'll post the console output when it finishes. I can tell you that there weren't any errors shown.
I updated and rebuilt, and now it works. It was either a dependency problem, a fix I didn't have, or a local modification that I removed (in any case, it's not currently a bug).
verifying based on bryner's latest comments