I've never used the guru program, but as general knowledge, WPA has two types of keys.
One is a hex string (A hex passcode will have nothing other than 0,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f)
The other is a plain text which can include any letters.
Based on the error, it sounds like what you entered is a plain text key but your program was expecting a hex key. You might check the settings to see if there is an option somewhere to switch between the two key types (You often have to tell it which type of key you are going to tell it, otherwise it defaults to the wrong one)
PM me or something if needed, although as noted, I'm not familiar with this specific software.
In use: Chargriller Pro w/ Firebox | Ugly Drum Smoker (BPS Style) about to enter the fray