Are you testing the new cairo, pango, atk, and gtk2 extensions? That would require not installing gtk+-2.tcel, simply creating an empty file "touch /usr/local/tce.installed/gtk+-2.tcel" and then installing gtk2.tcel and it's deps.
It sounds like you have one of two issues. The first is you have run out of loop devices. That is remedied when booting with the "tinycore max_loop=222" boot code. 222 is easy to type and gives you lots of loops. Or you are having a conflict with libraries. The conflict is possible, but as pango.tczl is a newer pango than is included in the gtk+-2.tczl it would not cause problems. I am running with the newer atk, pango, pixman, cairo and gtk2 along with emelfm2 and all my usual gtk2 apps.
My bet is the loop device limit is reached since a library conflict should not happen with those two extensions. Not to mention that tcz's do not overwrite each other or system files by default.