This is a common confusion with the old WEP-encryption. The actual key is either 40 or 104 or 128 Bit large. Togeter with the 24 bit IV (initialization vector) this yields 64 / 128 / 152 bit total. Some manufacturers include, some exclude the IV. So it might be well working when you set the Cisco device to 40 Bit and the other to 64 Bit. They possibly mean the same.
i tried the 40bit and did not work. For some reason the AP the vendor supplied uses 64bit encryption. It has 64 and 128 enabled on it so I am trying to get it all figured out. Some sites says i can change the code so that it will also do 64bit too. The vendor wants too much money to supply one as a backup. Trying the cheap way first.
Your encryption is set to 64 bits hex. As Patrick says, this is 40 bits key + 24 bits IV, so 40 bits and 64 bits are the same... but your client may be set to use 64 bits ASCII, not hex. The format in which you enter the key also counts. I would suggest making sure you use the same format on both sides, probably ASCII is easier...