The fact this has only happened on weekends and when using the guide is probably a coincidence.
You should reboot your receiver to see if that fixes the issue. If not...
What you described is a symptom of a signal issue somewhere between your receiver and the Cox server. When you press a button on the remote, a command request is sent to the Cox server which sends a response back to your receiver. A signal issue can cause the receiver to lock up waiting for a response from the server that it never receives. While watching a crystal clear channel, does your receiver ever freeze when you press pause, reverse or fast forward? If the answer is yes, you should schedule a tech visit to check your signal. If your cable comes in from a pole, be sure to request a tech with a long ladder. The tech should check your signal at the tap to determine if there's a main line issue. If the issue is on Cox's side of the demarc, you won't be charged for the tech visit.