It is time to make the upgrade to 1255F, the newest update to rFactor. All rFactor races from October 23rd on will use 1255F

Download from rFactor.net or Race2Play

Jerry Chen gives some great advice on how to handle this update: (Thanks JC!)
Before you install, just in case, you will want to make a backup of \userdata\[your player name] folder. You should be doing that anyways, but do it now.

Note: Find your original activation email. (not the unlock code email, but the "Thank you for your order" email from Trymedia systems Inc. Inside, find the "Activation code", it'll be really long string of letters and numbers in all lower case, no dashes. When you launch 1255F for the first time, it'll ask you to "Try free" or "buy". Don't click on those.

Look down in the bottom right hand corner of the window, there will be a link that says "Already paid?". Click on that, and it'll ask you to reactivate. You'll need the Activation code, and the email address the activation code was sent to.

If you do not have your original activation email from Trymedia, you may get the activation code online from the Trymedia support site

ISI's notes:

The rFactor 1255 patch (build F) was created to address some online security issues, add additional overall stability, and match the new retail DVD version recently released in Europe. 1255 F offers a significant improvement in game peformance over rFactor 1250.

The update consists of:

* rFactor.exe
* rFactor Dedicated.exe
* Plugins\NetCommUtilPlugin.dll
* Updated Sounds

PLEASE NOTE: You will be required to reactivate rFactor if you upgrade to v1255. Before you do this, locate your original confirmation email. Make sure you can locate your Activation Number, Order Number and email address used. If you need a new confirmation email sent out to you, visit TryMedia.

Download the update from any mirror site. First move the original files into a \Backup directory. Unzip the contents of the update ensuring you replace all files. Once you run the new version of rFactor, it will ask you to Buy/Unlock. Follow the Already Paid link at the lower right of the first purchase screen, using the Activation Number and email address from the confirmation email.

If you need to have your email changed or your activations reset, please send a request to purchase at rFactor net

FAQs

Q: Can I play online with people who have the retail DVD.
A: Yes, so long as you have upgraded to v1255.

Q: While this update work if I have v1150 or below?
A: No, this update will only work on v1250.

Q: Is there a full install for v1255.
A: There is a retail DVD version of 1255 and a digital version will be made available in the future.

Q: I updated to an earlier 1255, do I need to update to the final F build?
A: Yes, update to the F build. No re-activation is required.

Data Acquisition plug-in suposedly ain't working with v1225. Can anyone confirm?

All servers have been updated to v1255F

Tested it on GP79 server, works!

Cannot renew the license online had to contact Trymedia. :(

A tip that worked for me: if rFactor freezes after you click 'Already paid?' and you're using Kerio 4 or newer, uninstall it and try again. Just quitting Kerio was not enough.

Luckily Gmail has option to put a star beside important e-mails.s

Any idea what to do when the e-mail address used at purchase is now dead & buried?

You could try sending Trymedia an e-mail stating the transaction number (from your creditcard bill or Paypal, or any payment method really). Worked for me :-)