The spec for the 1841 says that it will support 8 VLANs using 802.1q on 12.4T version of IOS, and although this is not a trunk, the limit of 6 is strange.
You don’t normally configure the IP address on the interface, there should be one for each VLAN configured on the sub-interface. Each VLAN should be a different subnet, and then the router provides the routing between them and the rest of the network. Otherwise there usually isn’t any reason to configure different VLANs.
Can you post the version of IOS you are using, and possibly the parts of the config relating to the VLANs? A diagram would also be useful, just a basic one, not huge detail outside the immediate connections to the router.
Then we can get a better idea of exactly what is in the config. Also post why you are doing this solution, so we may be able to propose alternatives.