Cannot understand Wireshark logs - .php errors



Somebody over at Ubuntu suggested using wireshark to nail my problem.

XP/Vista have no problems. However, in Ubuntu 8.1/9.04 and netbook remix, as well as PCLInuxOS, I cannot post to internet forums.

Opera sometimes works, but not always. Firefox never works.

I get timeouts or “Open/Save xxxx.php” dialogue boxes.

In short, Windows works fine, but with Linux all .php pages give me errors.

Wireshark logs nothing in XP. I have four logs from posting/failing to post in Linux.

I am a complete novice on networking, and the logs mean nothing to me. :?

Where do I start looking? I am hesitant to post the full logs as they provide hackable IP/MAC information.