It looks like this problem is inherited from the default install files of mirc itself. I did a fresh install of mirc 6.16, and i got something pretty similar.
If you edit popups.ini with notepad while mirc isn't running, you'll see each [section] having lines beginning like n0= n1= etc. For them to work correctly, each number should be in order, and they should appear only once.
Notice how your [lpopups] section has the n2= above the n0=, and you have 2 n6= lines followed by an n7= line, and then it repeats n6= and n7= again. You should re-number so there's not more than 1 line within each section having the same string to the left of the "=".
After getting rid of these dupes, see if your mirc starts behaving.