Frequent game crashes

Citronas

Since the last patch I'm experiencing more frequent crashes. About every third or fourth game is just crashing.

Autosending the generated crashlog doesn't work.

Here's the crash log:
Error: Couldn't open file ''
Error: Couldn't open file ''
Error: Couldn't open file ''
Loading config://ConsoleBindings.json
Loading config://FavoriteServers.json
Loading 'maps/ns2_refinery.level'
Error: Couldn't open file 'models/props/summit/oreconveyor_rail.model'
Error: Couldn't open file 'models/props/refinery/refinery_oreextractvert_temp.model'
Error: Couldn't open file 'models/cinematics/exoreveal/page_1_panels_1-11 - onosemerges/camera7.model'
Error: Couldn't open file 'materials/descent/descent_wall_02_a.material'
Error: No shader specified for material 'materials/descent/descent_wall_02_a.material'
Building pathing mesh for level maps/ns2_refinery.level
Finished loading 'maps/ns2_refinery.level'
Error: Couldn't open file ''
Error: Couldn't open file ''
Error: Sound 'ambient/spooky_music_summit' couldn't be loaded (Not enough memory or resources. )
Error: Couldn't open file ''
Error: Couldn't open file ''
Error: PhysX: User allocator returned NULL.