iMac (late 2009) Will Not Connect to "N" Network Anymore

Greetings:

Recently, my iMac (Late 2009) stopped connecting to my "N" Network. See below:

This seems to correspond with upgrading my router software (DD-WRT v24-sp2 (02/11/13) std (SVN revision 20675). The funny thing is that none of my other "N-capable" devices exhibit this same issue (i.e., my AppleTV 3G and iPhone 5 still connect with no problems).

Has anyone else run into this?

Pertinent info is as follows:

Model Name: iMac

Model Identifier: iMac10,1

Processor Name: Intel Core 2 Duo

Processor Speed: 3.06 GHz

Number of Processors: 1

Total Number of Cores: 2

L2 Cache: 3 MB

Memory: 12 GB

Bus Speed: 1.07 GHz

Boot ROM Version: IM101.00CC.B00

SMC Version (system): 1.52f9

Software Versions:

CoreWLAN: 3.0.1 (301.11)

CoreWLANKit: 2.0 (200.10)

Menu Extra: 8.0 (800.7)

configd plug-in: 8.0.1 (801.17)

System Information: 8.0 (800.1)

IO80211 Family: 5.0 (500.15)

WiFi Diagnostics: 1.1 (110.26)

AirPort Utility: 6.2 (620.33)

Interfaces:

en1:

Card Type: AirPort Extreme (0x168C, 0x8F)

Firmware Version: Atheros 9280: 4.0.70.23-P2P

MAC Address: 04:1e:64:f1:03:df

Locale: FCC

Country Code: US

Supported Channels: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 36, 40, 44, 48, 52, 56, 60, 64, 100, 104, 108, 112, 116, 120, 124, 128, 132, 136, 140, 149, 153, 157, 161,

Local Wi-Fi Networks:

...

xxxxxxxxxxxxxxxxxxxxx - 5G:

PHY Mode: 802.11n

BSSID: c0:3f:0e:90:f0:61

Channel: 64,-1

Network Type: Infrastructure

Security: WPA2 Personal

Signal / Noise: -38 dBm / -96 dBm

....