Cookies not being sent back and forth properly in Opera

Double quotes are formally illegal in a cookie value. If you escape them as %22 it will work.

Have you checked if this is an issue with cookie domains ? I'm assuming you're using Javascript to set/read the cookies ? In any case there are 4 cookie domain issues that you might want to check (I know I've had these issue with an old FF version):

1 - check for illegal cookie characters: allowed cookie characters you might not be allowed to use '-' or '=' in the cookie name, and you shouldn't use non-ASCII characters in cookies at all. A base64 encode might deal with this.

2 - check that the domain on which you set your cookie (via javascript code or any other way) is identical to the domain on which the code is executed.

3 - check that the cookie domain is not localhost; see if you can test setting the cookie from a remote domain

4 - if you're using JS to set your cookies, try testing if you can set the cookie with a CGI in your browser to make sure it's not a browser issue. If it works which it should, see if you can read the cookie using JS (as opposed to setting it).

Let me know how this goes in the comments, I've dealt with similar issues a number of times and depending on what you get with these checks, I'm pretty sure I can help you fix the issue.

Looking at those Opera screenshots, they seem to be AJAX / XHR requests which are processed within the same second. Is it possible that Javascript is triggering both of those requests "simultaneously", so the response from the "first" is not arriving before the request for the "second" is constructed - and therefore the cookies have not yet been set?

I'm not familiar with the technologies/toolkits you're using, so don't know if these are stock code or part of your custom application.