Handbrake crashes on startup

I'm running Windows 7 32 bit, I get the following error when opening Handbrake:

An Unknown Error has occured.
System.Runtime.InteropServices.ExternalException (0x80004005): A generic error occurred in GDI+.
at System.Drawing.Image.Save(Stream stream, ImageCodecInfo encoder, EncoderParameters encoderParams)
at System.Drawing.Image.Save(Stream stream, ImageFormat format)
at Growl.CoreLibrary.ImageConverter.ImageToBytes(Imag e image)
at Growl.CoreLibrary.Resource.op_Implicit(Image image)
at HandBrake.ApplicationServices.Functions.GrowlCommu nicator.Initialize()
at HandBrake.ApplicationServices.Functions.GrowlCommu nicator.Register()
at HandBrake.ApplicationServices.Services.Encode..cto r()
at HandBrake.ApplicationServices.Services.QueueProces sor..ctor(Int32 instanceId)
at Handbrake.frmMain..ctor(String[] args)
at Handbrake.Program.Main(String[] args)

Any ideas?