SQL & PL/SQL :: Script Hangs When Deleting From Table

I'm testing a procedure which loads data into my database, and after each test I want to empty some of the tables and reset the sequences. I have this script to do that...

DELETE FROM COM_MERGE;
COMMIT;
DELETE FROM COM_TITLE;
COMMIT;
DELETE FROM COM_ISSUE;
COMMIT;
DELETE FROM COM_PAGE_ELEMENT;
COMMIT;
DELETE FROM COM_ELEMENT;
COMMIT;
DELETE FROM COM_STORY_TITLE;
COMMIT;
BEGIN
COM_RESET_SEQUENCES;
END;

Today I added the call to the sequences procedure to my script, but I have been using the script to delete from tables for a number of days without problem.However today I am finding that when I run the script it works ok the first couple of times, but when I try running it for a third time, it hangs after the second delete (in other words it stops when it gets to the delete from COM_ISSUE). After this happened the first couple of times I stopped the db and restarted it, then the script was ok twice, but again I'm finding that the script hangs. There is no error message, but the script fails to complete.

I didn't know if it was because originally I had one commit at the end of the script, so I added commits after each delete but that didn't solve it.I am using SQL Developer but I have found the same problem when running the script from SQL Plus.This is the definition of the COM_ISSUE table (just in case the table is the source of the problem).There is only one row in COM_ISSUE.

CREATE TABLE "BILL"."COM_ISSUE"
(
"CI_ID" NUMBER NOT NULL ENABLE,
"CI_TITLE" NUMBER NOT NULL ENABLE,
"CI_DATE" NUMBER NOT NULL ENABLE,
"CI_PRICE" NUMBER NOT NULL ENABLE,
"CI_PUBLISHER" NUMBER NOT NULL ENABLE,
CONSTRAINT "COM_ISSUE_PK" PRIMARY KEY ("CI_ID") USING INDEX PCTFREE 10 INITRANS 2 MAXTRANS 255 COMPUTE STATISTICS STORAGE(INITIAL 65536
[code]....