More info, after many tests:

F10-Snapshot 3 installed on an Acer Aspire One - kernel 2.6.27.3-34rc1 - wireless worked, but there was no wired connection.  At the next boot the wired connection worked, but wireless was lost, and has not worked since.

Typical event - First it offers me the chance to connect to hidden networks.  I give it the ESSID, set it to WPA and give it the passphrase.  It whirs for a while, then a 
dialogue box opens asking me to give a WEP key.  There is no option to set the WPA key this time.

Kernels tested since that date:
2.6.27.4-79
2.6.27.5-94
2.6.27.5-100
2.6.27.5-109 -  all i686

/etc/sysconfig/networking/devices/ifcfg-wlan0 says
# Atheros Communications Inc. AR242x 802.11abg Wireless PCI Express Adapter

On several occasions NetworkManager has reported a successful link, but at 0%.  Further investigation shows that it is to a different subnet.  At no time has any 
other network been listed by NetworkManager, and the nearest other wifi network does not use the IP range mentioned.  Also, it reports that it is connected to my ESSID.

'service network status' gives

Configured devices:
l0 eth0 wlan0
Currently active devices:
lo eth1 wmaster0 wlan0

lsmod | grep ath gives
ath5k		 17164	0
mac80211	112520	1	ath5k
cfg80211	 23816	2	ath5k,mac80211

nm-tool                                                                            

NetworkManager Tool

State: connected

- Device: eth1 
----------------------------------------------------------------
  Type:              Wired                                                     
  Driver:            r8169                                                     
  State:             connected                                                 
  Default:           yes                                                       
  HW Address:        00:1E:68:BD:EF:73                                         

  Capabilities:
    Supported:       yes
    Carrier Detect:  yes
    Speed:           100 Mb/s

  Wired Settings

  IPv4 Settings:
    Address:         192.168.0.92
    Prefix:          24 (255.255.255.0)
    Gateway:         192.168.0.1       

    DNS:             192.168.0.1


- Device: wlan0 
----------------------------------------------------------------
  Type:              802.11 WiFi                                                
  Driver:            ath5k_pci                                                  
  State:             disconnected                                               
  Default:           no                                                         
  HW Address:        00:22:33:44:55:66     #obscured                                     

  Capabilities:
    Supported:       yes

  Wireless Settings
    WEP Encryption:  yes
    WPA Encryption:  yes
    WPA2 Encryption: yes

  Wireless Access Points
---
 iwlist scanning
lo        Interface doesn't support scanning.

wmaster0  Interface doesn't support scanning.

wlan0     No scan results

eth1      Interface doesn't support scanning.

pan0      Interface doesn't support scanning.

---
ifconfig wlan0

wlan0     Link encap:Ethernet  HWaddr 
00:22:33:44:55:66
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 
frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 
carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
---
iwconfig wlan0
wlan0     IEEE 802.11bg  ESSID:""
          Mode:Managed  Frequency:2.412 GHz  Access 
Point: Not-Associated
          Tx-Power=27 dBm
          Retry min limit:7   RTS thr:off   Fragment thr=2352 
B
          Encryption key:off
          Power Management:off
          Link Quality:0  Signal level:0  Noise level:0
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid 
frag:0
          Tx excessive retries:0  Invalid misc:0   Missed 
beacon:0
---

On one of those 'bogus connections' - 
Running iwconfig wlan0 again I now get

wlan0     IEEE 802.11bg  ESSID:"myESSID"
          Mode:Ad-Hoc  Frequency:2.412 GHz  Cell: 
36:8F:3A:45:3F:BC
          Tx-Power=27 dBm
          Retry min limit:7   RTS thr:off   Fragment thr=2352 
B
          Power Management:off
          Link Quality:0  Signal level:0  Noise level:0
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid 
frag:0
          Tx excessive retries:0  Invalid misc:0   Missed 
beacon:0
---
Running the connection again, changing the ad-hoc to Infrastructure (the only other option, Managed being absent) the connection was lost and could no longer be found.
---
The best I ever achieved was

wlan0     IEEE 802.11bg  ESSID:"myESSID"
          Mode:Managed  Frequency:2.412 GHz  Access 
Point: Not-Associated
          Tx-Power=27 dBm
          Retry min limit:7   RTS thr:off   Fragment thr=2352 
B
          Encryption key:off
          Power Management:off
          Link Quality:0  Signal level:0  Noise level:0
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid 
frag:0
          Tx excessive retries:0  Invalid misc:0   Missed 
beacon:0

It has been suggested that this may be a kernel bug affecting the ath5k driver.