Emulator

What steps will reproduce the problem?

1. Using the D3D plugin, loading the game. OpenGL seems to crash too.
2. Playing a level - I've tested Woodward Camp and the Trainyards at least
3. Playing for around a minute, sometimes longer.

What is the expected output? What do you see instead?

The game runs nicely, aside from the crashes. If you wait to see a rider on
the selection screen, Dolphin will chuck up an error "VarToD3D: Invalid
Type / Size Combo 0, 4" followed by "Failed to create D3D vertex
declaration". This same error is displayed at the start of every level.
These can be dismissed and the game is very playable, until it crashes
either around 30 seconds in, or a little later if lucky. Sound is also
quite slow on the menu screens, although they're running at ~50fps

What version of the product are you using? On what operating system?

Windows 7 32bit, Dolphin SVN revision 5141; I've had the same experience on
the earlier recent revisions too though.

Please provide any additional information below.
Running a Core 2 Duo @ 3.2ghz, HD4850, windowed resolution 1152x864.
Fullscreen 1280x1024.