Hi Sam
"I'll investigate this problem and try fall back to single threaded if not many CPU cores available."
Thanks for the info and indeed, that might be welcome.
I have just done a ruthless cull of programs that I don't use and in particular those that were set to run at startup. (Using CCleaner)
The processor usage has now dropped from 52% on average when the machine was not in use (apparently) to 1% when running Firefox browser; Videopad and this forum together!
I shall run a re-edit on a recent project and see how VP 4.45 now performs. Loading files still pushes it up to 100% but it produced the TNs in the media list window in only a few seconds and then dropped back to 0-5%. (Instead of 51%) Adding clips to the timeline produced a similar result. (Up to 100% and back down again after less that 30 seconds)
Processor is now running at 1-2%. A vast improvement. 
It may be something to suggest to those users who have experience stoppages and very slow performance. OK I know it's a logical thing to do........... 
Nat