glGetString(GL_Version) does not return anything

[a333klm]

Hello :),
I have two threads executing the following:

SoDB::init();
render_action = new SoGLRenderAction(this->render_viewport);
render_action->setTransparencyType(SoGLRenderAction::SORTED_OBJECT_BLEND); 
uint32_t uniqcc = SoGLCacheContextElement::getUniqueCacheContext();
render_action->setCacheContext(uniqcc);
autoclipbboxaction = new SoGetBoundingBoxAction(this->render_viewport);
offscreen_renderer = new SoOffscreenRenderer(this->render_action);

In one thread a call after that to glGetString(GL_Version) returns the correct OpenGL Version.
The other thread returns nothing.

Outside of VirtualBox the code works as intended and glGetString gives information. I know that a Virtualbox is not a usual setup.
Maybe someone has an idea what could be the issue with OpenGL here.

Thank you very much.