[dba-SQLServer] Table lock with uncommitted BeginTrans

Hi all

A table didn't respond at the client's SQL Server.
The dba told that it was locked by a uncomitted transaction, and a restart of the SQL Server was needed. That happened and the table was accessible again.

This table, however, is only used by an Access app via ODBC, and nowhere is BeginTrans used for the table. As to my understanding, SQL Server performs AutoCommit if not told otherwise.

So, questions:

1. How can a BeginTrans be applied without a RollBack/CommitTrans?
2. Is it really necessary to restart the SQL Server to unlock the table?

Any other suggestions what to look for or how to prevent this situation?

/gustav