Opengl errors when plotting merlin data

[NickDraper]

This has been reported from the Merlin cabin PC
Tatiana Guidi 24/02/2011

When loading the file and plotting the MERLIN instrument I get the following error messages (run number 9643):

*** Run title: quiet counts - all doors -vacuum on from 3.6e-5 mbar ***
Loading geometry cache from C:\MantidInstall\instrument\MERLIN_Definition.vtp
Load successful, Duration 2.92 seconds
OpenGL error detected in GLViewport::issueGL(): invalid enumerant
OpenGL error detected in GL3DWidget::mouseMoveEvent: invalid enumerant
OpenGL error detected in GL3DWidget::mouseMoveEvent: invalid enumerant
OpenGL error detected in TexObject::generateTexture()[delete texture] : invalid enumerant
OpenGL error detected in TexObject::generateTexture()[delete texture] : invalid enumerant
OpenGL error detected in TexObject::generateTexture()[delete texture] : invalid enumerant
OpenGL error detected in TexObject::generateTexture()[delete texture] : invalid enumerant
OpenGL error detected in TexObject::generateTexture()[delete texture] : invalid enumerantOpenGL error detected in GLViewport::issueGL(): invalid enumerant
OpenGL error detected in TexObject::generateTexture()[delete texture] : invalid enumerant
OpenGL error detected in GLViewport::issueGL(): invalid enumerant

[NickDraper]

This issue was originally trac ticket 2542