Can't make POST requests while using a wireless connection

[Nolifer]

This is a weirdo problem.
I've installed Mint and he have successfully discovered my wifi. I am able to browse the web, make GET requests and simple POST requests but when I try to make a request with the form enctype as "multipart/form-data" it fails.
Also, when I try to login on Pidgin or use Transmission it doesn't works.

PS: Everything works correctly on a wired connection, but it's NOT my wifi router because everything works right in Windows.

[veggen]

I am so very sorry for saying this, but... YES!!! THANK GOD I"M NO LONGER THE ONLY ONE!!!
Back to the subject. I've been experiencing a very similar problem since Mint 12. I've tried to replicate it in other Ubuntu based distros and generally succeeded.

Now, my issue is not *exactly* the same but similar enough. I can not do POSTs when my firewall is up and when I'm on VPN (with or without firewall). Haven't tried WiFi, but I have a feeling it would fail too.
Here are my findings:

* Some forms work. I can login to this forum, but not post.
* When firewall is up, and I restart networking (/etc/init.d/networking restart) POSTs work for a while and then stop for no reason
* When on VPN, nothing helps
* Timing seems important. One time everything worked normally on VPN but after a reconnect, I never got it to work again.

[Nolifer]

Dude, after 40h~ without sleeping I found the soluction. I'm sorry for my bad writing and typing, but I'm really tired.
I've downgraded the kernel, upgraded the kernel, tried to use ndiswrapper, tried to code my own drivers to the a9k, called the Atheros support and nothing worked. I was going to bed now and then I realized that I could just sniffer the packets and see what's going on under the network layers.
Started the Wireshark and made the sniffer follow all packets from my wireless network card. Made a simple post, made some GET requests and then made a post with a non default enctype; saw that the connection between the wireless router and the pci was correctly made and the packets were fully sent, but between the router and the modem it was broke, so I discovered that my router is breaking the packets at all.
Just accessed the router's configs and changed the MTU rate to 1400, everything works well now!

[veggen]

You, my man, are magnificent I did what you said and POSTs now work for me when the firewall is up. VPN still kills them though, but at least I solved my most immediate problem.
I found out that my modem had MTU of 1400 (per ISP's instructions) and wireless router (that the modem is connected to) had 1500. Now that both have 1400, it works better.