Old URLs not working?

[GateKeeper]

I have htaccess for the 5.0 Beta on my test site but an old URL similar to this

Message - Reeftalk Reviews

Generates the same error as this does on reeftalk.

"We're sorry, but the system experienced an unrecoverable error. Please try again later."

I always try to test on reeftalk before reporting this issue in case I'm all wet.
Thank you.

[GateKeeper]

Should the htaccess not also handle conversion from this
Message - Reeftalk Reviews
to the new format?
This URL also generates the same error.
Thank you.

[Chuck S]

Dry-Goods Dealers - Reeftalk Reviews

The category urls redirect fine

Now I might have had an old file on my site I simply uploaded a clean showproduct file it seems to redirect fine

IslandAquatics.com - Reeftalk Reviews

[GateKeeper]

I should have taken screen shots of reeftalk, since this is where I picked up the error code. I downloaded a new copy of Beta 3 on the 24th. Have you updated showproduct.php since then? Clearly something changed from the time I reported this issue.
Does this rely on cookies at all?
The problem on reeftalk appears to have gone away, but I still have the problem on my test site. Any suggestions?
Thank you.

[Chuck S]

I haven't changed anything that I am aware of

You should just make sure your htaccess and showproduct files are current