I think I finally found the cause. I enabled global log and that is helping me see more details. Looks like ShowEQ is picking up my mumble traffic and firing on it sometimes. Digging through the code I found that 0x500 opcode is session disconnect. And right at the time of my last packets in zone log I see a 0x500 opcode picked up going mumble server -> my client.
I hid the IP, but here's what it looks like. This log is about 100ms after my last zone log entry.
Code:
Jan 24 2013 22:21:40:311 [<My Mumble Server IP>:7506->client:58368] [Size: 110]
[OPCode: 0x500]
000 | 00 05 61 99 9b 7a da 72 6e e5 42 90 e7 90 88 87 | ..a..z.rn.B.....
016 | 86 d8 95 87 0e 81 e6 a0 59 48 b7 19 95 10 ef c4 | ........YH......
032 | 66 79 c2 23 c6 e2 62 b9 33 97 c0 6a c2 49 cf b4 | fy.#..b.3..j.I..
048 | 1e 02 05 6d 33 6c a8 c8 c6 5d 05 0c e3 39 19 fc | ...m3l...]...9..
064 | f4 e1 5f 21 e1 c7 fb 61 a7 3a 84 01 a0 86 f0 c7 | .._!...a.:......
080 | 57 3c b3 ea fe 9b f5 29 83 fa 90 18 23 cc 52 e0 | W<.....)....#.R.
096 | af bf 36 07 39 df 6f a3 1c ee 42 46 d3 af | ..6.9.o...BF..
So now I just need to figure out a way to block my mumble server IP address from being ready by ShowEQ.