I've seen similar issues simply by using Linux as my main desktop... some sites just won't work because of it, or seem to filter out "Linux" in the user agent. Which kinda sucks.
Could you give an example? I've been working with a Linux desktop since 2009 and everything seems to work.
This is one of the reasons why all of my browsers identify as a recent Chrome version. All of those problems just up and disappear. I started doing that when Google claimed (lied) that some of their products no longer support Firefox and would block me from accessing right up until my browser identified itself as Chrome. No bugs, no issues.