Since ASE 11 (I cannot remember if it was with the very first release of 11, but certainly not before) the password column in syslogins has been encrypted. Setting this column to NULL does not equate to that login having a NULL password. A NULL password still requires the correct binary string to be in place.

In release 12 and above, set the minimum password length to be 0 using sp_configure and give that account a null password, and all should be fine.

Before 12, it is not possible to set the minimum password length, so the direct approach is not possible. So, update the relevant record in syslogins setting the password column to be the same as that of an account with a NULL password already.

How does one get the correct binary value? When a new ASE is built, the 'sa' account has a NULL password to start with. Setting an account to have the same binary value as such an 'sa' account should work. Remember that the binary string is going to be specific to the operating system and the exact release of ASE etc. Obviously, if you have set the password of your 'sa' accounts to be something other than NULL (sensible move), then you are going to have to build yourself a dummy server just to get the correct string. If this is important to you, then you may wish to store the value somewhere safe once you have generated it.