Cisco IPSec VPN Client Session gets disconnected at randon times from remote ASA5505

We have a number of users connecting / terminatiing Cisco IPSec VPN Client sessions onto a Cisco ASA5505  appliance.

The users are using a variation of Client OS, XP, Vista etc and different versions of the Cisco IPSec VPN Client. What is ahppening is, the clients are getting disconnected from the ASA at randon, sometimes after 5 minutes, 15 minutes even 7 hours. The logs off the Cisco VPN Client show the below,

Cisco Systems VPN Client Version 5.0.05.0290
Copyright (C) 1998-2009 Cisco Systems, Inc. All Rights Reserved.
Client Type(s): Windows, WinNT
Running on: 6.1.7600
7      10:08:25.162  03/08/11  Sev=Warning/2 CVPND/0xA3400015
Error with call to IpHlpApi.DLL: CheckUpVASettings: Found IPADDR entry addr=10.4.9.189, error 0
8      10:08:26.176  03/08/11  Sev=Warning/2 CVPND/0xA3400015
Error with call to IpHlpApi.DLL: CheckUpVASettings: Found IPADDR entry addr=10.4.9.189, error 0
9      10:08:27.190  03/08/11  Sev=Warning/2 CVPND/0xA3400015
Error with call to IpHlpApi.DLL: CheckUpVASettings: Found IPADDR entry addr=10.4.9.189, error 0
10     10:08:28.204  03/08/11  Sev=Warning/2 CVPND/0xA3400015
Error with call to IpHlpApi.DLL: CheckUpVASettings: Found IPADDR entry addr=10.4.9.189, error 0
11     10:08:29.218  03/08/11  Sev=Warning/2 CVPND/0xA3400015
Error with call to IpHlpApi.DLL: CheckUpVASettings: Found IPADDR entry addr=10.4.9.189, error 0
12     10:08:30.232  03/08/11  Sev=Warning/2 CVPND/0xA3400015
Error with call to IpHlpApi.DLL: CleanUpVASettings: Was able to delete all VA settings after all, error 0
13     10:08:31.043  03/08/11  Sev=Warning/2 IKE/0xA3000067
Received an IPC message during invalid state (IKE_MAIN:512)

Any feedback would be great...