Expression/Query editor warped

First of all, many thanks to Rajesh for his post giving the solution for 8.6.1. I shamelessly copied the symptom images to save time. However, I was not able to leave him an according message there.

Symptom

I work with PowerCenter 9.1.0 Hotfix 1 and at times my expression and query editors get warped. It looks like this.

Unlike Rajesh I did not experience the right hand side of getting lost which might look like this.

Solution

You can either wipe your regestry completely with the side effect of having to enter repositories and such again.
Or, you fix your registry. I recommend you to back up your registry beforehand. You have to 0 out the positions of the editors and their splitter. Apparently, it is not at the same place in the registry as in 8.6.1 (Rajesh's solution).
Then, it looks like this.

If you backup your fixed registry setting for that spot, you can import it, if it happens again and are done quite easily.
For PowerCenter 9.0.1, you could save the following into a .reg file to import it when ever you want.

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Informatica\PowerMart Client Tools\9.1.0\Designer\Options\Global\Editor\SQL]
"Keywords"="pmkeywd.ini"
"Chroma"=dword:00000001
"Extra word chars"=""
"Comment"="0,0,0"
"Keyword"="0,0,255"
"Quote"="255,0,0"
"SQuote"="255,0,0"
"Default Text"="0,0,0"
"Background"="255,255,255"
"Comment Start 1"=""
"Comment End 1"=""
"Comment Start 2"=""
"Comment End 2"=""
"SQL Editor Font"="Courier New"
"Expression Editor Font"="Courier New"
"SQL Editor Font Script"=dword:00000000
"Expression Editor Font Script"=dword:00000000
"Case"=dword:00000000
"Tab size"=dword:00000008
"Show tabs"=dword:00000000
"Expression Editor Position"=hex:00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,\
  00
"Expression Editor Splitter Position"=hex:00,00,00,00,00,00,00,00,00,00,00,00,\
  00,00,00,00
"SQL Editor Position"=hex:00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00
"SQL Editor Splitter Position"=hex:00,00,00,00,00,00,00,00,00,00,00,00,00,00,\
  00,00
"Base Editor Position"=hex:98,00,00,00,0f,00,00,00,ec,03,00,00,1b,03,00,00

Joiner XYZ must have exactly two inputs.

Symptom

You get the error even if  your mapping joiner has exactly two inputs but at least one of them is a mapplet.

Reason (possible)

I do not know for what reason Informatica made this restriction.
I imagine the OUTPUT transformation to be sort of a virtual transformation, a placeholder as the mapplet transformation is. If you imagine the mapplet in the mapping being replaced by the content of the mapplet (like you can choose in the debugger) WITHOUT the OUTPUT transformation, you end up with more than two inputs for the joiner.

Solution

Create a collector expression as only input to the mapplet output.

Uselessness of set variable functions

The setting of the new value of a mapping variable is only at the closing of the session done such that one cannot use mapping variable to provide values between target load groups.
Also, it is not possible to use the mapping variable with the new value later in the same target load group. There, however, you just can forward the port of the set variable function as it returns the new value.

Session Log File directory = $PMSessionLogDir/$PMWorkflowName/ and the like do not work

Yeah, you cannot use all built-in variables/parameters for the log file configuration, even though they are known at the time of initialisation and could be set. Why is not clear to me but apparently they are not yet set then.