chunk loading

I am playing Minecraft at a friends house. We are on the same internet. This internet has a filter called clean router. the internet provider is Comcast. (I don't know if this makes any difference, but tmi is better than to little info) I am playing on a windows pc, he on a Mac. on the server It seems like only a set number of chunks load. I can only walk so many blocks in any direction before it becomes just a cliff with void on the other side I have to reload the server to continue. After I exit and re-enter the world, I can continue for about the same number of blocks. Now here is the weird part: my friend on a Mac can see and interact with the parts I can't.

I know this is old version, and this might be fixed, but on the off chance it's not, I am reporting this.