We have seen this issue in SP2 but only with W2008 clients. We have a open case with LANDesk support since july and still we are experiencing this problem randonly when deploying the agent. We recover from the issue after rebooting the affected server
Turns out the newly built SP3 agent was picking up the fact that LANDesk HIPS was checked in our LANDesk Firewall configuration. BUT, we only have Management Suite, not Security Suite, so it shouldn't have cared what was checked. We had Security Suite a year or so back and the HIPS option must have been checked then.
Still no reason why it only affected certain Windows 7 computers (XP didn't care).
I know that it may not be possible, but have you tried running the wscfg32.exe manually located on the ldlogon? I was having the same issue on one particular Windows 7 box and manually running the install worked for this issue. Just don't forget that this installs your default agent configuration. So if you have a special config set it as the default, run wscfg32, and switch back to your original default configuration. Good luck.