FYI, here's what I did:

DBCC DBREINDEX was sufficient to fix the error like the following:

Server: Msg 8951, Level 16, State 1, Line 1

Table error: Table 'MSmerge_contents' (ID 1957582012). Missing or invalid key in index 'nc4MSmerge_contents' (ID 4) for the row:

Server: Msg 8955, Level 16, State 1, Line 1

Data row (1:20154:9) identified by (RID = (1:20154:9) tablenick = 2236004 and rowguid = 55EA2ACD-1475-4F0C-953B-E76A2CBAC33BØ™¨) has index values (rowguid = 55EA2ACD-1475-4F0C-953B-E76A2CBAC33B`¢¨ and tablenick = 2236004 and rowguid = 55EA2ACD-1475-4F0C-953B-E76A2CBAC33B`¢¨).

However, to fix error like the following, a DBCC CHECKDB with REPAIR_ALLOW_DATA_LOSS was required:

Server: Msg 8964, Level 16, State 1, Line 1

Table error: Object ID 658101385. The text, ntext, or image node at page (3:407121), slot 4, text ID 145881235456 is not referenced.

In fact, after I did the DBCC CHECKDB with REPAIR_ALLOW_DATA_LOSS, and I ran the checkdb again, one index of one table still had error.  I had to redo the DBCC DBREINDEX on that particular index and that fixed the problem.

baes