Here are some things to try if you haven't already:
1) Update DirectX
Every new version of DirectX contains bug fixes so if you are having trouble, this should be your first step. You can get the latest version from Microsoft's Website directly here
2) Run a File Check
The 3rd option on the launcher 「ファイルチェック」 is used to check that all game files are present on your system. If anything is missing, it should download it automatically. It will also replace any files that may have been modified, intentionally or otherwise.
3) Update your drivers
your video card driver! Check with the manufacturer of your video card. Many manufacturers have programs which can automatically identify and install the most recent driver for your card.
For AMD/ATI: http://support.amd.com/us/gpudownloa...to_detect.aspx
For Nvidia: http://www.nvidia.com/Download/Scan.aspx?lang=en-us
4) Free up space on your hard drive
Try freeing up at least 2GB of space on the hard drive where you have PSO2 installed - This will typically fix graphical errors and loading issues, but can also fix other problems as well.
5) Disable your firewall to see if it fixes the problem
Incorrectly configured firewalls/antivirus programs can cause issues with PSO2. If you're having an issue, and have already tried the steps above, please disable your firewall and antivirus, and try running the game again. If it works, you'll need to add an exception in your firewall/antivirus program for PSO2.
6) Reduce your graphics settings
Some graphics cards and PSO2 don't play nice together. Try going into the options menu「環境設定」(2nd option in the launcher) and lowering the slider to 1. If this fixes your problem, go back into the settings, raise it to the next number, then try again, until it starts having the issue again. Once it starts having the issue again, set it back to the previous working number.
Switching to Simple Shaders
Some people have reported success using this, even if the above instructions did not work.
In the options, click 描画 and check the option in the screenshot below
Then click the bottom left option to save and the bottom right option to return to the launcher.
7) Avoid permission issues
With the introduction of Windows 7/8, Windows has gotten really upset about permissions and ownership and such. This has caused a number of problems with games, and other programs.
Copy the entire folder where you have PSO2 installed (Typically "C:\Program Files\SEGA\PHANTASY STAR ONLINE 2\" or "C:\Program Files (x86)\SEGA\PHANTASY STAR ONLINE 2\") and paste it on the root of your drive (So it's now C:\PHANTASY STAR ONLINE 2\"). Try running the launcher/game from there instead, and see if it works.
If it does, simply make a shortcut to the pso2launcher.exe in the new folder and replace the default shortcut it made in the start menu during the installation.