Your situation indicates that one of your applications is doing 2-phase commit with an external transaction coordinator. What you see in systransactions is a coordinated transaction which has not been completed.
The status of "Prepared-Detached" shows that something started a transaction, but is no longer connected to the system. ASE has no way to decide whether to commit or rollback the work done - and it will maintain that state after a reboot.
Unless the originating process can reconnect and complete the original coordinated transaction, your only option is to use the DBCC commands to force completion. Note - you must choose whether to commit or rollback the transaction - I hope you have some way to tell which of those actions is correct 
When I have done this in the past, there has been no way to find out which is right - so I tend to err on the side of rollback.
Hope that helps.
Antony.