I had this type of issue what a 100gig db that I was trying to back up. It would get so far and then the backup seemed to just hand but never fail. I opened a ticket with microsoft and we ended up finding it to be a hardware error. I cannot remember what it was though as that was over 2 years ago.

Not sure if this is of any help but here are two queries to check on the status:

SELECT A.NAME,B.TOTAL_ELAPSED_TIME/60000 AS [Running Time],

B.ESTIMATED_COMPLETION_TIME/60000 AS [Remaining],

B.PERCENT_COMPLETE as [%],(SELECT TEXT FROM sys.dm_exec_sql_text(B.SQL_HANDLE))AS COMMAND FROM

MASTER..SYSDATABASES A, sys.dm_exec_requests B

WHERE A.DBID=B.DATABASE_ID AND B.COMMAND LIKE '%BACKUP%'

order by percent_complete desc,B.TOTAL_ELAPSED_TIME/60000 desc

SELECT A.NAME,B.TOTAL_ELAPSED_TIME/60000 AS [Running Time],

B.ESTIMATED_COMPLETION_TIME/60000 AS [Remaining],

B.PERCENT_COMPLETE as [%],(SELECT TEXT FROM sys.dm_exec_sql_text(B.SQL_HANDLE))AS COMMAND FROM

MASTER..SYSDATABASES A, sys.dm_exec_requests B

WHERE A.DBID=B.DATABASE_ID AND B.COMMAND LIKE '%RESTORE%'

order by percent_complete desc,B.TOTAL_ELAPSED_TIME/60000 desc

SELECT r.session_id,r.command,CONVERT(NUMERIC(6,2),r.percent_complete)

AS [Percent Complete],CONVERT(VARCHAR(20),DATEADD(ms,r.estimated_completion_time,GetDate()),20) AS [ETA Completion Time],

CONVERT(NUMERIC(10,2),r.total_elapsed_time/1000.0/60.0) AS [Elapsed Min],

CONVERT(NUMERIC(10,2),r.estimated_completion_time/1000.0/60.0) AS [ETA Min],

CONVERT(NUMERIC(10,2),r.estimated_completion_time/1000.0/60.0/60.0) AS [ETA Hours],

CONVERT(VARCHAR(1000),(SELECT SUBSTRING(text,r.statement_start_offset/2,

CASE WHEN r.statement_end_offset = -1 THEN 1000 ELSE (r.statement_end_offset-r.statement_start_offset)/2 END)

FROM sys.dm_exec_sql_text(sql_handle)))

FROM sys.dm_exec_requests r WHERE command IN ('RESTORE DATABASE','BACKUP DATABASE')

----------------------------------------------------------------------------------------------------

USE MASTER

--

SELECT SESSION_ID, '[' + CAST(DATABASE_ID AS VARCHAR(10)) + '] ' + DB_NAME(DATABASE_ID) AS [DATABASE],

PERCENT_COMPLETE, START_TIME, STATUS, COMMAND,

DATEADD(MS, ESTIMATED_COMPLETION_TIME, GETDATE()) AS ESTIMATED_COMPLETION_TIME, CPU_TIME

FROM SYS.DM_EXEC_REQUESTS

--Apply this Where Clause Filter if you need to check specific events such as Backups, Restores, Index et al.

WHERE COMMAND LIKE '%BACKUP%' OR COMMAND LIKE '%RESTORE%' OR COMMAND LIKE '%INDEX%' OR COMMAND LIKE '%DBCC%'