Can't access wp-admin from my MAC (but only my mac!)

Four months ago I employed a wordpress developer to create a wordpress website for me (www.toomanycheekydogs.com.au). She did a fantastic job and it was all going great until a couple of weeks ago when I stopped being able to access the website AND the wp-admin site (toomanycheekydogs.com.au/wp-admin) from my home MAC. All I get is a blank white page when I try to log in to both. It doesn’t seem to be the browser because it happens using both safari and chrome and I didn’t change any settings on wp to trigger it. The weird thing is that both websites can be accessed through other computers. IT’s only my home MAC that is blocking them.

The problem started around the same time as I changed modems. Could it have something to do with having a new IP address?

help! I’m really frustrated about this.

Johanna