[mivayan]

There can only be one global of each type active at any time. So if you had another 'Strands' active he would have dispelled it.

I believe it works like this when you cast a global enchantment.
1) If there are 0-4 globals, a free slot is taken.
2) If there are 5 globals, something else happens.
3) If there are 5 globals, rule #1 does not hold true ever again. This is the bug mentioned by Nephelim