When you obtain the CLK signal from ORing the WR with A15, writing to other devices could trigger the 374. The problem is perhaps that the address of the 374 is not specific enough.
The output of the 73LS32 will go low when: A15 is low (which I presume is almost always in your program) and WR is low.
It could be that you have a timing problem here as well because the data is latched at the END of the write cycle.
I suggest you to get a 74HC138 and look at my earlier post to connect that.