This is not unusual if since moving the unit there are things such as walls, doors, etc. involved. Push come to shove you could look into getting a wireless access point.
...the signal strength dropped by 50% to a speed of 24 Mbps
I have a 11n 150 mbps router and a USB 11n 150 mbps adapter.
Before I had my laptop 5 feet away and there was no problem of course. Now there is no longer direct line of vision.
I did speedtests that confirm the loss of signal strength.
I changed the router configuration to Channel 11, speed: 11n only. (not auto b/g/n)
Any adjustments I can make?