A family of Microsoft word processing software products for creating web, email, and print documents.
Issues with double-clicking Word document icons would usually indicate a problem with file associations; repairing Office would then fix the issue permanently. Of course, the strange thing here is that it happens only for documents in certain locations.
The fact that the issue is intermittent makes it difficult to troubleshoot.
Are you running some sort of third-party "cleaning" software (such as CCleaner) and, in that case, are you letting it modify the registry?