1. Because it is trying to /open/write/save - there may be a permissions error. This can happen when a plugin is not given the write permissions necessary to complete the program request. Are there any plugins that you installed that requested any sort of write permissions?
2. Also note that the first error is an open error -- if a plugin is requiring any sort of path information, make sure that this is correct.
3. Resource allocation my have been depleted before the script finished. In this case you would need to set the memory and php parameter a bit higher. There are several threads in the community that discuss the best ways to do this. It may depend on whether you are on a managed wp server or cPanel.
4. Corrupted plugin/theme - If this occurred after an update, you may need to delete and reinstall any recently added updated plugins.