Oracle Express intermittently stops responding, requiring a OS reboot to fix
You are encountering these problems because you are running a 32-bit version of Oracle XE on 64-bit Windows. This is not a supported configuration, and is known to have many documented problems.

Due to there not being a 64-bit version of XE, you can instead install the Standard Edition (free for development) from here. If you're also using APEX, you can get it here.