long lasting select, no io nor cpu usage ?

Hi,

I have a table (sanact) with 23.125.525 rows (and a hundred columns).
I am doing a select, that did not finish after some 15 hours... Select
is as follows:

select * from sanact where sanact___rfovsnide = 'MYVERSION' order by
sanactcsu;

There is an index on sanact___rfovsnide and doing EXPLAIN shows it is used.
Resulting dataset should be 1626000 rows.

iostat shows 99.5% idle disks, almost no activity.
top shows almost no cpu usage.

Where should I be looking for a problem ?

Thanks in advance,

Franck