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Does the password reset link take you to Tanki's website or to miniclip?
Are you sure you're entering the correct Flashplayer link(s) for Tanki?

If you are, try clearing the cache of your default browser.
This also happens to me. Like TriNitroToIuene said, the solution for me is to just refresh the page using "F5" on your keyboard or by clicking the icon in your browser's address bar. Of course, only do this after waiting for about 30-45 seconds for the battle to load, and after you refresh once, give it plenty of time again. :)
That might be the issue. Try testing your internet speed here: I believe that a minimum of 3MB's per second is recommended for most online games. If you're getting less than that, try some of these tips:

  • If you're using WiFi, move closer to the Wireless access point (router).
  • If you're using WiFi and the above tip doesn't help, connect using a wired (Ethernet) connection.
  • Reboot your modem/router.
  • Upgrade your internet (contact ISP to do this).

However, if you're internet meets the minimum recommendation, the only thing left that might help is uninstalling and reinstalling Adobe Flash Player.
Not major ones, at least that I've heard of.
That's because, unlike the forum, you need to create your StarLadder account when you first enter their website.

Use the same nickname that you have in Tanki Online though ; ). 
You need to go to first. If it automatically logs you into an account, click the  icon in the upper-right corner and click "Yes" when it asks you if you want to quit. It should display the homepage. Now click on "Play", and it should display the login screen. Next time, don't check the "Remember me" box if you wish to be asked to login to your account(s) every time you open Tanki Online.
I'm not exactly sure what causes this error, I have experienced it before, but I can give you some solutions that have worked for me:

Clear your browser cache if you're using a browser (Firefox, Internet explorer, etc.)

If you're using Flash Standalone and that still doesn't solve your issue, trying clearing your shared objects.
Try disconnecting and then reconnecting your computer's internet first (by unplugging the Ethernet cord or disconnecting from the WiFi, and then reconnecting the plug/reconnecting to the WiFi).
If that doesn't help, reboot/restart your modem (and/or router if you're using WiFi). And as an extra measure, you could try clearing your browsers cache, although I doubt that has anything to do with it.

If none of the above solutions help, try testing your internet's speed at I believe a minimum of 3 MB's per second is recommended for online games. If you have less than that, you may need to consider upgrading your internet connection (contact your ISP to do this).
It is a complex process that exceeds my knowledge. Really, probably only the developers know this exact information.