Thank you for submitting your reduced test case TBK.
NOTE: The correct result when the rectangle is clicked on is 145px. This is because the rectangle's left position is relative to its new parent AFTER
mergeTBObjects() is applied. However, since ToolBook does not support this kind of dynamic restructuring of its content, it falls back to its own way of figuring out the position. In non-IE browser it so happens to work correctly, but in IE you get an incorrect, or unexpected, value.
Since you were using
pgTBObjGet() to return the left position of the rectangle, you should've been able to get the correct value regardless of browser, etc. However, our port of this function relies on ToolBook's internal function to get this information and thus the bug persisted. I have fixed this for future releases of the PowerPac (v12.332+).
A workaround that works in all browsers is to use the PowerPac function
pgGetStyle() as it reads directly from the DOM instead of relying on any internal ToolBook content features.