2.0: "The ConnectionString property has not been initialized."

[RAM]

Hello,
On SomeDataList.DataBind() I receive InvalidOperationException

"The ConnectionString property has not been initialized."

In a few places above same SomeDataList.DataBind() commands work fine;
database is connected, connection string used is correct ("Data
Source=PC\SQLEXPRESS;Initial Catalog=MIMMagazynDemo;Integrated
Security=True").
How to diagnose the problem? Please help!
THANX
/RAM/