Trigger Update Syntax

I€™ve developed a trigger for SQL 2000 that works great in my test environment, but is a bit inconsistent in my production environment. The goal of this trigger is to find and update the row that was just entered in the OCNTACT2 table. It takes the highest integer value from CONTACT2.UPRONUM (yes, it€™s an nvarchar field), increments it by one, then updates the CONTACT2.UPRONUM field for the newly inserted row.
Does anyone see anything wrong with this trigger? Thank you for reading.
CREATE TRIGGER Update_UPRONUM_For_Webgrabber
ON CONTACT2
AFTER INSERT
AS
BEGIN
SET ROWCOUNT 1
UPDATE CONTACT2
SET CONTACT2.UPRONUM = CAST(C.tempColumn AS int) + 1
FROM CONTACT2 CROSS JOIN
(Select top 1 cast(upronum as int) as tempColumn from CONTACT2 AS CONTACT2_1 WHERE
(UPRONUM NOT LIKE '%[,]%') AND (UPRONUM NOT LIKE '%[a-z]%') AND (UPRONUM NOT LIKE '%[A-Z]%')
order by cast(upronum as int) desc) AS C
WHERE (CONTACT2.UPRONUM IS NULL OR CONTACT2.UPRONUM = '') AND (CONTACT2.UCOMPBY = 'WEB')
AND (CONTACT2.UWEBDATE > '12/13/2007')
SET ROWCOUNT 0
END