What steps will reproduce the problem?
1. I'm not sure what specific configuration of Prat is required, but when I have Prat and Deadly Boss Mods installed simultaneously, the issue reproduces. Disabling DBM lets things work fine. SO: I went to www.deadlybossmods.com and they say:

"A lot of people are currently reporting that DBM breaks their chat on the PTR when using a chat mod like Prat. This is not a bug of DBM. The reason for this problem is that Blizzard updated their chat filter API and the latest alpha version of DBM already makes use of this updated API. But many chat mods still use the old chat filter API, making them incompatible with every mod that uses the new one."

2.
3.

What is the expected output? What do you see instead?
When I whisper people I expect to see my "To <toon>: blah blah blah my whisper." Instead I get nothing (no line at all).
When I receive whispers from people I expect to see "From <toon>: blah blah blah their whisper." Instead I see "From <toon>:". I see that someone sent me a whisper, but not what the whisper text was.

What version of the product are you using?

*IMPORTANT* -> Can you reproduce the problem when ONLY Prat is running?
No -- it is a conflict between Prat & DBM. The authors of DBM say it is not a bug with DBM, that it is due to a new chat filter API that Blizz released. Since they're actively developing their mod, I'm inclined to believe they looked into the problem.

Do you play on US or EU. What language do you use?
US, English.

Do you have an error log of what happened?
No, I'm afraid not. There *is* no error log, but I don't run a bug grabber while on my main, which is the toon that uses both Prat and DBM together.

Please provide any additional information below.