Hey Damir,
If ":b0:b1" isn't 2 separate bind variables, it would appear to be an illegal name for one, as shown in SQL*Plus:
SQL> variable b0:b1 number
SP2-0553: Illegal variable name "b0:b1".
SQL>
How are you expecting Toad to treat it? Does SQL*Plus treat it the same way as Toad?
You also reference two recent versions of Toad -- did older versions work differently?
Let us know!
Rich