When assigning Static IP Addresses you should make sure that they are outside of the DHCP range of the router but within the subnet.
For example a typical router configuration would look like this:
Default Gateway - 192.168.1.1 - This is the routers IP Address
Subnet - 255.255.255.0 - This gives your current subnet 256 available IP addresses
DHCP Range - 192.168.1.2 to 192.168.1.100 - This means you can dynamically assign up to 99 IP Addresses out of 256
PC1 - 192.168.1.2 - DHCP/dynamically assigned
PC2 - 192.168.1.3 - DHCP/dynamically assigned
TV - 192.168.1.4 - DHCP/dynamically assigned
Printer1 - 192.168.1.101 - Statically assigned
Printer2 - 192.168.1.102 - Statically assigned
Try confirming that your static IPs are outside of the DHCP range on your netgear and see if the problem is resolved or not. DHCP also has leases that it issues to each assigned device. If a device goes offline the DHCP feature will reserve that IP Address for XXX hours/minutes. After the lease expires that IP will become available to the next device. Sometimes you can bump up your lease times and avoid IP conflicts, although usually folks want lower lease times to refresh thier machines more frequently.