So you are saying that once you just load the SEQ, that the program freezes? Even before you play the file?
Or can you open the FX window on the affected track click on "none" in the selected VSTi line on the plugin list. And then go to the "Remove Plugin" button and erase the entry.

If this doesn't work, and it sounds like it doesn't, then I'd probably close the file and use "Search" to find the VSTi in question and change it's name by adding "X" to it. Then reopen the file and see if runs without the VSTi. If it does, then remove the VSTi and resave.

Hope this helps. Ian

Ian
My "Original Tunes" Site
My gene pool needs more chlorine.