you should be able to simply log into the router config, go to the encryption page then on all the routers i have setup it shows the encryption key there, but if it doesn;t just add a new one, i doubt you would need the original key just to change it
Lee 
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My PC: Core2Duo E6300 @ 1.86 Ghz, Asus P5v-VM DH , 200 GB Maxtor SATA ,2GB (2*1GB Kingston DDRII), Radeon x1650 Graphics (256 mb), 2* Acer 17 inch TFT's, Windows Vista Home Premium
Server: AMD Athlon XP 2800+ 256 Mb Ram, 8Gb IDE for o/s, 2 * 250GB SATAII for storage, Ubuntu Server 7.10
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