ERROR 1030 - got error 124 from storage engine

[fabio stirpe]

I have the following problem. using the query:

SELECT reurl, date FROM redirect
WHERE url = 'XXXXXX.yyy'

The redirect table has 350,000 rows and the query has a running time of about 0.25 sec.

THE QUERY must be repeated about thirty times per page. the result is catastrophic. The column 'url' has an index. If I do a EXPLAIN I have:

TABLE SELECTTYPE ---- ---- ---- POSS_KEY TYPE KEY ---- ---- ---- KEY_LEN REF ---- ---- ROW USING
SIMPLE reurl ----------- ----- ----- ALL NULL NULL ----------- ------ ---- NULL-NULL -340980 - Using where

If i use FORCE INDEX on the query

SELECT reurl, date FROM redirect FORCE INDEX(url)
WHERE url = 'XXXXXX.yyy'


I have the following error:
ERROR NO. 1030 got error 124 from storage engine

but doing a EXLAIN
EXPLAIN SELECT reurl, date FROM redirect FORCE INDEX(url)
WHERE url = 'XXXXXX.yyy'
i have:

TABLE SELECTTYPE ---- ---- ---- POSS_KEY TYPE KEY ---- ---- ---- KEY_LEN REF ---- ---- ROW USING
SIMPLE reurl ----------- ----- ----- reurl ref reurl ----------- ------ ---- 257-const --- 10 - Using where

that is what I expect.
But, Why the SELECT does not work? Why not be executed properly?