What steps will reproduce the problem?
1. Have Prat running.
2. Set "new whispers" to "new tab" in the Blizzard social options.
3. Verify that this works as expected. (eg: new whispers pop up in a new tab.)
4. Install WIM
5. Set the formatter to "Prat" because you do lots of text mangling with it.
6. Be super-excited.
7. Whisper yourself a message like "wow, this wim thing is, like, super-awesome!"
8. Wonder why you only see the timestamp in that.
9. Turn off the timestamp option in the WIM formatting.
10. Observe that you now see absolutely nothing in the WIM whisper window.
11. Start to debug the code.
12. Wonder if maybe it is some oddity about Prat, new whisper tabs, and WIM not playing nice, even though those new whisper tabs don't show up.
13. Turn off the Blizzard option to put new whispers in a separate tab.
14. Whisper yourself.
15. Celebrate your great victory, as your prat formatted text shows up exactly as expected! Yay!

What is the expected output? What do you see instead?

As noted: I expected to see the whispers, but I saw nothing from the wim/prat combination in the window. It clearly saw there was a message, because it injected timestamps for send and receive, but it didn't manage to get the text.

I checked the "HTML" and "BBCode" formatted versions, and they were equally certain that there was absolutely no text present in the message.

What version of the product are you using?

Current releases of both: WIM 3.6.12 and 3.5.7

Do you have an error log of what happened?

I checked carefully, and there are no errors logged -- it just silently fails.

Please provide any additional information below.

I am sure that not all those steps are required, but they were what happened for me to reproduce this. My day job is writing software, so I can debug this more if you need -- I am not super-familiar with WoW lua, but can likely manage whatever you need.