Resource starvation can cause this sort of error.  Is it possible that the host server is out of memory?  Some VPS providers configure their VPS images without a swap file, so when the VPS image is out of memory, instead of starting to swap, processes that take up too much memory are killed. In such a situation, creating a swap file can be a quick fix, but increasing the server capacity would be a much better solution, as swap on VPS tends to be extra slow. Some commands that can help to check available resources, but which are only useful before the OpenERP process dies:

free -m

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ps axu