Boom:
---------------------------
Adventure Game Studio
---------------------------
An unexpected error occurred. Please post the following information on the AGS Technical Forum.
System.Runtime.InteropServices.External
Exception: GDI+ is not properly initialized (internal GDI+ error).
at System.Drawing.Graphics.FromHdcInternal(IntPtr hdc)
at System.Windows.Forms.PaintEventArgs.get
_Graphics()
at System.Windows.Forms.Control.PaintBackC
olor(PaintEventArgs e, Rectangle rectangle, Color backColor)
at System.Windows.Forms.Control.PaintBackg
round(PaintEventArgs e, Rectangle rectangle, Color backColor, Point scrollOffset)
at System.Windows.Forms.Control.PaintBackg
round(PaintEventArgs e, Rectangle rectangle)
at System.Windows.Forms.Control.OnPaintBac
kground(PaintEventArgs pevent)
at System.Windows.Forms.ScrollableControl.
OnPaintBackground(PaintEventArgs e)
at System.Windows.Forms.Control.PaintWithE
rrorHandling(PaintEventArgs e, Int16 layer, Boolean disposeEventArgs)
at System.Windows.Forms.Control.WmEraseBkg
nd(Message& m)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.ScrollableControl.
WndProc(Message& m)
at System.Windows.Forms.ContainerControl.W
ndProc(Message& m)
at System.Windows.Forms.UserControl.WndPro
c(Message& m)
at System.Windows.Forms.Control.ControlNat
iveWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNat
iveWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.Callb
ack(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
---------------------------
OK
---------------------------
And this:
---------------------------
Adventure Game Studio
---------------------------
An unexpected error occurred. Please post the following information on the AGS Technical Forum.
System.AccessViolationException: Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
at System.Drawing.SafeNativeMethods.Gdip.I
ntGdipDeleteMatrix(HandleRef matrix)
at System.Drawing.SafeNativeMethods.Gdip.G
dipDeleteMatrix(HandleRef matrix)
at System.Drawing.Drawing2D.Matrix.Dispose(Boolean disposing)
at System.Drawing.Drawing2D.Matrix.Finaliz
e()
---------------------------
OK
---------------------------
I just tried to change the main background of a room with this 24bit png:

edit: I have just recovered the installation of Microsoft .NET Framework Version 2.0, and now it works.
Sorry for bothering.