INFORMATION_SCHEMA.ROUTINES or syscomments are not reliable.
The text field is nvarchar (4000) for both (only for systems with multiple lines). Thus, your search text may be lost at the border for systems or never found for INFORMATION_SCHEMA.ROUTINES
sys.sql_modules .definition - nvarchar (max)
SELECT OBJECT_NAME(object_id) FROM sys.sql_modules WHERE definition LIKE '%mytext%'
Edit, October 2011
Updating this answer.
Red Gate SQL Search is a free SSMS plugin that is very useful.
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