Resolution:
When testing a BWC application, customer experienced problem that one of the IcWorkers "hangs" (i.e. does not return from) the following statement: "delete  from TASK_DEPENDENCIES  where PARENT_ID in (select PARENT_ID  from TASKS where JOB_ID=:b0)"
Subsequently all other workers queue behind that IcWorker's unrelesed lock until the BWC server stalls completely.

Oracle Statistics job seems to have a strong involvement in this issue.
When the job runs concurrently with the BWC application, customer was able to reproduce the problem, not in a deterministic way, but say in about 80% of all test runs (Oracle says that the job should usually run at times where there is no or little application activity, but there is no guarantee that it will finish within that window). When the job is disabled and existing Oracle statistics are deleted prior to running the test, they were are not able to reproduce the problem.
Oracle filed a bug on this issue.

Customer applied a patch provided by Oracle for Oracle 10.2.0.2 that seems to have fixed the described problem.

Here is the info from Oracle's Metalink for your records:
---------------------------
Remove the patch for bug 5116440 and install the new merge bug fix:
Merge 5722731 on top of 10.2.0.2 for Bug 5667683 Bug 4722645 Bug 4712638
-----------------------------

When BWC 5.3 (IC 7.2) is used with Oracle 10.2.0.2 (with patch for bug 5116440), it will result in IcWorker hanging.