Another thing to note is that when you were getting -45, its wayyyyy to strong.
Your ideal signal is between -55 and -70. Once you go over -50 you will damage the radios inside the router and your laptop over time. Much like people, if they shout at each other, they will go deaf. I especially laugh at mac users who use the built in wireless of their desktop mac to connect to a router less than 50cm away.
-45 is higher than -50 which is higher than -70 because they are numbers below 0 which not alot of people realise.
As a side note, has anyone noticed how some new telecom routers come with their transmit power turned down slightly (configurable in the web options)
I think this is to lower urban noise in the 2.4ghz band and increase performance.