I have the same problem on vanilla FC10. NetworkManager-gnome doesn't dynamically acquire IP addresses from the router via DHCP, and the connection only works if I set a static IP. But then I get speeds only up to 20KB/s (pretty much the same as bug #451422 ). The network keys (I use WPA) are changed (as mentioned in this report before). The real key is made of 8 letters, but they are changed to a hash of some sort that has 64 symbols. Using seahorse makes no difference, as when changed, the NetworkManager asks me about the key again, and changes it to the hash again. But seeing that I can still use the Internet (with a static IP and 20 KB/s), maybe that's intended?
I've also tried switching to KNetworkManager (actually, now both Gnome and K managers are installed, and they work as one :) ), and it's the same.

Finally I've attempted to make the connection manageable by the system-config-network instead of NetworkManager, but it seems it doesn't support WPA keys at all. Then I tried WPA Supplicant, but it needs DHCPD, and initially DHCPD is empty; I have no idea how to configure it manually. All my attempts here failed.

lspci shows my network devices:
00:1f.6 Modem: Intel Corporation 82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M) AC'97 Modem Controller (rev 03)
02:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL-8139/8139C/8139C+ (rev 10)
03:00.0 Network controller: RaLink RT2500 802.11g Cardbus/mini-PCI (rev 01)

iwlist wlan0 scanning (when online, doesn't work offline):
wlan0     Scan completed :
          Cell 01 - Address: 00:1D:7E:BC:C6:F4
                    ESSID:"linksys"
                    Mode:Master
                    Channel:11
                    Frequency:2.462 GHz (Channel 11)
                    Quality=48/100  Signal level:-70 dBm
                    Encryption key:on
                    IE: WPA Version 1
                        Group Cipher : TKIP
                        Pairwise Ciphers (1) : TKIP
                        Authentication Suites (1) : PSK
                    Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 18 Mb/s
                              24 Mb/s; 36 Mb/s; 54 Mb/s; 6 Mb/s; 9 Mb/s
                              12 Mb/s; 48 Mb/s
                    Extra:tsf=0000010f49b5018a
                    Extra: Last beacon: 42ms ago

ifconfig:
wlan0     Link encap:Ethernet  HWaddr 00:02:44:AF:65:51
          inet addr:192.168.1.101  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::202:44ff:feaf:6551/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:11 errors:0 dropped:0 overruns:0 frame:0
          TX packets:34 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:2233 (2.1 KiB)  TX bytes:5772 (5.6 KiB)

iwconfig:
wlan0     IEEE 802.11bg  ESSID:"linksys"
          Mode:Managed  Frequency:2.462 GHz  Access Point: 00:1D:7E:BC:C6:F4
          Bit Rate=1 Mb/s   Tx-Power=24 dBm
          Retry min limit:7   RTS thr:off   Fragment thr=2352 B
          Power Management:off
          Link Quality=69/100  Signal level:-62 dBm
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:0   Missed beacon:0

So, overall I think there are two bugs here: DHCP not working and NetworkManager storing and displaying hashed keys instead of the actual key.