It would be great if you could close this thread out by posting what the issue was if you figured it out, so other users will know. I suspect the other MVP poster was on the correct track as nothing else really comes to mind unless perhaps the QVD had a conflict related to read/write in that if a process has it open for read, and another process tries to write, the write will fail, as it cannot get the exclusive lock in that case, and vice versa as well, except the read fails due to the write process having the exclusive lock already. Multiple concurrent reads can occur just fine, but not a read/write combination. The odd thing was the error, would be curious to know what the Task log returned and the script log should have been the same error info, but probably worth confirming to be sure. If you do post what it was, you can then use the Accept as Solution button on the post if it was something not related to the other post.
To help users find verified answers, please do not forget to use the "Accept as Solution" button on any post(s) that helped you resolve your problem or question. I now work a compressed schedule, Tuesday, Wednesday and Thursday, so those will be the days I will reply to any follow-up posts.