PDoughboy has come up with a comprehensive guide to using a VPN to download and play the game if your internet provider is causing you to have incomplete downloads or preventing you connecting to some areas.
First of all, this workaround will work for two issues as I see it: 1) If your ISP is preventing you from downloading/patching certain files and 2) If you suspect your ISP is preventing you from loading certain areas due to their filtering
There is a relatively simple solution for this, and can be done several ways. The primary method to solving these problems is by either downloading the game through a VPN Connection or playing the game over a VPN Connection, depending upon which problem above you are having. If you already have access to a VPN or know how to attain one, there is no need to continue with the steps below.
There are many options when it comes to downloading VPN Clients. Personally I chose VPNBook, which is completely free and hosted in Romania, so there is no way your ISP will block anything. You can download VPNBook here: http://www.vpnbook.com/#pricing or just follow the steps below.
1) Download the OpenVPN GUI software here: http://openvpn.net/index.php/download/community-downloads.html and choose your file type to download (i.e. exe, zip)
2) Install the OpenVPN GUI software and open the readme for reference
3) You now need to download a VPN Certificate file:
UDP & TCP: http://www.vpnbook.com/free-openvpn-account/VPNBook.com-OpenVPN-Euro1.zip
4) Unzip the certificate files and place the contents in the OpenVPN directory "Config" folder (example: "C:\Program Files\OpenVPN\Config")
5) You are now ready to run your OpenVPN GUI which should have created a shortcut on your desktop. It will be running in your taskbar at the bottom right when opened. Right click the OpenVPN icon in the taskbar and click "Connect".
6) When it prompts you for a username and password, use the default one provided by VPNBooks website. This has changed, so you may need to update your login details:
username : vpnbook
password : (for up to date passwords, visit here and click the 'OpenVPN' tab, the details are at the bottom of the drop-down tab)
7) It may require you to enter your username and password a second time. If it does, just re-enter the same username and password. If you are having trouble connecting still, try downloading the TCP Certificates from the link above and replace your old UDP Certificate files in the OpenVPN Config Folder with the TCP ones.
Now that you are on a VPN connection, you are effectively bypassing anything your ISP may be blocking or filtering which can cause errors during downloading or patching of the game, or simply not allowing you to run certain instances of the game itself.
If you are having trouble downloading or patching the game (certain files not downloading) follow the instructions Chris from GGG has provided on this post (running Content.ggpk Reclamation) while you are connected to the VPN: http://www.pathofexile.com/forum/view-thread/15283
If you are having problems running the game in certain instances (i.e. Microsoft Visual C++ Runtime Errors, or Exceptions) it may be a result of your ISP filtering while you are loading a specific area. You can solve this problem by connecting to the VPN and playing the game or trouble areas while on the VPN Connection.
If you have any further questions about anything regarding this tutorial, dont be afraid to PM me (PDoughboy). I hope this solves any issues you may be having. Happy Hunting!