Frankan9, This is going to sound strange, but give this a try: Set your WiFi router passphrase to 13 characters. Not at least 13, but 13 exactly (no spaces), and see if it helps.
Also make sure there are no spaces in the router SSID name.
Years ago at the computer shop we learned that for some reason the algorithms used for WiFi security are more compatible with more devices using a 13 character passphrase.
Adding a second router setup as a repeater, closer to your MAK, may also help with this.
3) Password strength or passphrase length only comes into play if you are using old WEP encryption, that's the reason the old computer store trick still worked:
-WEP 64bit requires 40 bits (from a given password) + 24 from an initialization vector; 40 bits means 10 hexadecimal digits or (as a restriction) 5 ASCII characters you type in.
-WEP 128bit: requires 104 bits (from a given password) + 24 bit from the Initialization Vector; hence the given password can have 26 hexadecimal digits (4*26=104) or - as a particular case - 13 ASCII characters you type in.
Change your encryption to WPA. If it doesn't have it as an option, the equipment is wicked old, (circa 2003+) time for a new one.