10.6.7 - High wifi latency on Mac Mini (from mid 2007)

Question

Hi!
I have a MacBook Pro from mid 2009. It is upgraded to 10.6.7 and works with absolutely no problems. However I also have a Mac Mini from mid 2007 and since upgrading to 10.6.7 the wifi latency has been extremely high--averaging 5 seconds or more if I run a ping command on the IP address of my network gateway.
Last night I restored the system to its original OS X version (10.5) and the wifi worked great. Then I upgraded with my original Snow Leopard disc (10.6) and the wifi still worked great. Finally, I updated via the Software Updater to 10.6.7. The wifi instantly took on the high latency again. If I switch to my Windows installation via Bootcamp, the wifi works splendidly. The problem is definitely with 10.6.7. It is not with my Mac Mini hardware or with my router.
Some things I tried to resolve the problem (none of them worked):
I tried creating a new "Location" and reconnecting with that.
I tried zapping my PRAM
No need to delete my preferences files because I just did a complete OS restore
I have not changed my routers security settings because that is not an acceptable solution (some people suggest disabled WEP or WPA--I'm running WPA2).
Any help that you could provide would be great. I've never had a problem with Apple hardware or software before this, so this experience is disappointing.

Answer 1

Thanks for your response.
My router is a Linksys WRT160N.
I'm a little doubtful that it's just a matter of 10.6.7 and my router, since my MBP is currently running 10.6.7 and doing just fine. I'm fairly certain that the fault is primarily with 10.6.7 itself.
Here's the Airport information for my Mac Mini
  Software Versions:
  Menu Extra:    6.2.1 (621.1)
  configd plug-in:    6.2.4 (624.2)
  System Profiler:    6.0 (600.9)
  Network Preference:    6.2.1 (621.1)
  AirPort Utility:    5.5.2 (552.11)
  IO80211 Family:    3.1.4 (314.1.1)
  Interfaces:
en1:
  Card Type:    AirPort Extreme  (0x168C, 0x86)
  Firmware Version:    Atheros 5424: 2.1.14.5
  Locale:    FCC
  Country Code:    US
  Supported PHY Modes:    802.11 a/b/g
  Supported Channels:    1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 36, 40, 44, 48, 52, 56, 60, 64, 149, 153, 157, 161, 165
  Status:    Connected
  Current Network Information:
bsglwn:
  PHY Mode:    802.11g
  BSSID:    0:21:29:97:c:e4
  Channel:    6
  Network Type:    Infrastructure
  Security:    WPA2 Personal
  Signal / Noise:    -55 dBm / -96 dBm
  Transmit Rate:    54
Again, thanks for your help.