|In general, the wired connected computers do have internet access, no matter whether wireless option on the router is enabled or not.|
If the routers firewall gets under heavy stress, all traffic might be dropped.
This could happen, if one of the connected computers has a corrupt network card, that jabbers or, if a connected computer is infected by a virus and therefore causes heavy traffic through the internal and external (internet) network.
Btw.: It's always a good idea, to use a channel for wireless network, that does not exist in the direct environment.
E.g.: If there is another wireless network using channel 1, you should use a channel number 1+5, so channel 6.
If there is a wireless network on channel 6, use channel 1 or 11.