critical errors

[Fatality]

2010.3.29 09:19:27
OS : Windows XP 5.1 (Build: 2600)
CPU : GenuineIntel  Intel(R) Core(TM)2 Duo CPU     E7500  @ 2.93GHz @ 3437 MHz 1023MB RAM
Video : NVIDIA GeForce 8800 GTS (9621)
PosCode : LS8(83) 43352:-48299:-800 2/1 [398]

IDirect3DVertexBuffer9::Lock failed(80004005).

History: FD3DVertexStream::Cache <- FD3DRenderInterface::SetVertexStreams <- Render Things <- ATerrainInfo::Render <- this=21_16.TerrainInfo0 <- RenderTerrain <- RenderLevel <- FLevelSceneNode::Render <- FPlayerSceneNode::Render <- SceneNodeRender <- Draw <- UGameEngine::Draw <- UWindowsViewport::Repaint <- UWindowsClient::Tick <- ClientTick <- UGameEngine::Tick <- UpdateWorld <- MainLoop



I have W7 HP

[Udunnome]

I have the same graphic card and I sometimes get the exact same critical error.but it happens like 1/week or smthing