I to had the 'install stall' problem with both the security update on my 10.4.11 install and the 10.5.7 install on that HD..... Finally used ABD's link for the security update and that went right through...
For the 10.5.7 update persistence paid off.... had to try about 5 - 6 times... but finally it to went through with out a hitch....
We'll see what happens with use...
Bob K. rnkiii