According to LANDesk online help "Run from source" works with all packages types on UNC share. For HTTP shares, this option only works with SWD and MSI package types.
So what is your package type? If it's SWD or MSI you can still use HTTP share for "Run from source".
It is an executable capable of being installed in unattended mode. I would have done it the other way if I could get away with it, but the we want to test this as they suspect there are a few related to authentication, name resolution, and a few other things -- this way we are able to stay consistent.
I believe Paul indicated that if you use run from source that the credentials it uses to obtain the package and run it on the client is what is in preferred server credentials. Also, if you are using user mode to install the packages they will fail if the user is not a local admin. So are you using preferred server? Also you need to give Domain Computers access to the share. I would post the sdclient logs so we can take a look. If you are only having issues with two machines - then I would look at those machines and users logged on at the time of the installation. Do these users have access to the share?
you do not write which client os you have.
I think it is not a LANDesk problem. We've in the past the same problem on sites which uses one ghost image without using ghostwalker or NewSID... so they have the same SID
Try the following, start newsid (http://technet.microsoft.com/de-de/sysinternals/bb897418(en-us).aspx), reboot, and try the installation as Local System again...
(a other way was to delete the computer account from domain and add the computer again...)
Use a preferred server. That should take care of permissions issues.