Merged tickets slow or unable to load in browser

Yesterday, after merging two tickets, I attempted to click on the ticket
link in the queue to open the newly merged ticket to read. After a bit
of a wait, the browser displays an Internal Server Error message. This
morning, I find out that another user had this problem two or three
weeks ago with some tickets he merged.

I created four new tickets for testing. I merged the four tickets into
two separate tickets (I did them in different queues to see if that made
any difference). When I clicked on the ticket in the list, it took more
than 20 seconds but the newly-formed tickets displayed. I then merged
the two tickets into one ticket. After that merge, I receive the ISE
when I try to click on the ticket.

I’ve looked in the mailing list archives and saw a few others with this
question in the past 7 or so months, but most didn’t receive a reply. I
did find one where someone someone had luck by vacuuming the postgres
db. I tried that with no change in results.

I’m using RT 3.6.6 on Ubuntu 8.04 Hardy Heron with apache-2.2.8,
fastcgi, perl 5.10. Suggestions or is there any additional info that I
need to dig up to help you help me?