Let's recap...

i have a setup which looks like this

<Task A> --> ForEach(<TaskB>)

Task A produces Data which it stores in a Variable "v1" (AdoDataSet with exactly one DataTable in it)...

well yes, this is, as i explained, exactly what I'm doing

Sql is executed as "SQL from a variable".

The variable is a expression and contains the variable "FirstIdRunner" which is obtained from Task "A"

it's inside a second variable, scope of Task "B"

The variable contains a expression with a standard query containing exactly one variable... the one mentioned above