Cannot read block error.

I am running PostgreSQL 7.3.3 on OS X Server 10.2

The database has been running just fine for quite some time now, but 
this morning it began pitching the error:ERROR:  cannot read block 176 of tfxtrade_details: Numerical result 
out of range
any time the table tfxtrade_details is accessed.

A description of the table is at the end of this email

I have a backup from last night, so I haven't lost much data (if any), 
but I am curious if there is a way to recover from this (beyond 
restoring from backup) and how I would go about figuring out what 
caused it to prevent it from happening again.

I will keep a copy of the data directory if anyone wants me to do any 
analysis on it (I will need instructions).

Any insights would be appreciated.

Thanks

Jason Essington
jaessing@greenrivercomputing.com


hedgehog=# \d tfxtrade_details           Table "public.tfxtrade_details"    Column     |           Type           |
Modifiers
---------------+--------------------------+----------- rid           | integer                  | not null clientid
| integer                  | tradeid       | integer                  | rollid        | integer                  |
rollpct      | numeric(10,8)            | expdetailid   | integer                  | expid         | integer
     | contractpct   | numeric(10,8)            | contractamt   | numeric(18,2)            | origpct       |
numeric(10,8)           | origamt       | numeric(18,2)            | acctgperiod   | integer                  |
acctgperiodid| integer                  | editdate      | timestamp with time zone | edituserid    | character
varying(48)   | parentid      | integer                  | entityid      | integer                  | tradedate     |
date                    | maturitydate  | date                     | strategyid    | integer                  |
currencyid   | integer                  |
 
Indexes: tfxtrade_details_pkey primary key btree (rid),         tfxlinks_entityid_index btree (entityid),
tfxlinks_expdetailid_indexbtree (expdetailid),         tfxlinks_expid_index btree (expid),         tfxlinks_mdate_index
btree(maturitydate),         tfxlinks_parentid_index btree (parentid),         tfxlinks_strategy_index btree
(strategyid),        tfxlinks_tradeid_index btree (tradeid)
 
Triggers: RI_ConstraintTrigger_30891,          RI_ConstraintTrigger_30894,          tfxdetail_delete_trigger