Further, in all *.ui files, should all occurrences of QString be changed to TQString?
Yes.
A quick grep of the sources indicates a significant number of these corrections are needed. I'll start pecking at them.
To be sure I'm not making a mess, both of the following types of lines should be changed to TQString?
<signal>***(const QString&)</signal> <slot>***(const QString&)</slot>
There are many occurences of QString in many *.ui files in the full source. If these all should be changed could this be the cause of various bugs, such as What's This help tooltips no longer working in KControl?
It is possible, though there should be error messages in your .xsesson errors file regarding invalid connections in the affected modules if this is the case.
I tested tdebase by rebuilding with a patch and the xsession error disappeared. The patch did not resolve the What's This bug, but KControl functioned without incident.
Darrell