Frets on Fire error

Hello!

I've downloaded Frets on Fire, and played it once.
The second time I got an error: I removed the app and installed it again, but the arror is still there. (Now I'm on an other computer, but I'm stil at school and all the computers are the same.)
When I start the app, it says " See the logfile "E:\PortableApps\FretsOnFirePortable\App\fretsonfire\FretsOnFire.exe.log" for details", I click "ok" and the program quits.
I've made a copy of the log-file:

Traceback (most recent call last):
File "GameEngine.pyo", line 346, in run
File "GameEngine.pyo", line 320, in loading
File "View.pyo", line 183, in render
File "MainMenu.pyo", line 196, in render
File "Svg.pyo", line 643, in draw
GLerror: [Errno 1284] negatieve stackoverloop
Traceback (most recent call last):
File "GameEngine.pyo", line 346, in run
File "GameEngine.pyo", line 320, in loading
File "View.pyo", line 183, in render
File "MainMenu.pyo", line 196, in render
File "Svg.pyo", line 643, in draw
GLerror: [Errno 1284] negatieve stackoverloop

Does anyone know what the problem is and how to fix this?
It would be nice to play this at school.
Thanks!
xSandra