BUG #1487: Index problem

The following bug has been logged online:

Bug reference:      1487
Logged by:          Tom Yeh
Email address:      tom_m_yeh@yahoo.com
PostgreSQL version: 8.0.1
Operating system:   Windows XP
Description:        Index problem
Details:

I created an index for a table, say Entity, on a field, say id.

Then, the follwoing two SQL has different result:

select * from "Entity" e where e.id = '1000'

and

select * from  "Entity" e where e.id like '1000'

(The later uses sequential scan. BTW, while 7.4.x uses index why 8.0 behave
worse?)

Once I re-index it, the problem is gone. However, the problem comes back
randomly if I change some id.

The above can be replicated by using pgAdmin III only.