Trouble with models

Im having some difficulties with 3rd party model packs.
When i spawn things in theyre fine, however, when i save and return to a loaded project, all 3rd party objects have frozen, broken constraints and im unable to manipulate them at all.

Any workarounds ?
Has anyone else had this prob ?

There are no workarounds. Loads of people have this problem. Use Advanced Duplicator instead. To get it, download the Wiremod SVN using this tutorial: http://www.facepunch.com/showthread.php?t=688324