It's not unusual for some temporary files to refuse to go if they are connected with something that is maybe still active on the machine.
You can clean temps in other ways too.
Go to Start/Run and type in temp and click OK or hit the Enter key.
Then click Edit > Select All
Then click Shift/Delete simultaneously and OK any prompts after hitting the Enter key.
Some will refuse to go because they are pertaining to your current session, that's normal.
Repeat the exercise entering %temp% this time to clean even more.
As I said, some will refuse to delete, that's normal.
Also don't forget Windows has its own Disk Cleanup under Tools.