It seems that my GuiXT profile entries are destroyed. When I click on the profile button in GuiXT, instead of showing the profile window, GuiXT now opens a file guixt.ini      What is wrong?

In your sapgui folder there is a file  guixt.ini which contains the entry

IgnoreRegistry Yes

In this case GuiXT assumes that the profile parameters are maintained in the guixt.ini file. It suffices to put a comment sign "//" in this line. Please close all SAP sessions and logon again.