The Revenue Constituent Search by Lookup ID works differently in CRM 4.0 vs CRM 3.0. In CRM 3.0, the "Match All Criteria Exactly" check-box is defaulted to TRUE, whereas in CRM 4.0, it is defaulted to FALSE.
We're currently evaluating this issue for a fix in a future patch or service pack.
Steps to Duplicate
1. Select Batch entry from the Revenue functional area 2. Select an Enhanced Revenue Batch and click edit 3. Click the search button in the lookup ID field 4. Note that the match all criteria exactly box is not checked