The best way to solve your problem is to go to the “Options” menu, and click on “Prefrences…”. Go to the “Editing” tab and you will see 3 checkboxes at the top. I suggest that you UN-CHECK the “Enable looping on events by Default” option. You should then CHECK the “Collapse loop region when no time selection is present” option. Things should get easier.
Here are some other things you might want to be familiar with, concerning “looping” and selecting areas:
When what you described occurs, you can press the “loop Playback” button on what Vegas calls the “Transport Bar” (Immediatly under the timeline) Another thing that’s nice to know is if you right-click what Vegas refers to as the “Marker Bar” (this is the bar right above the timeline and the ruler) you have the option to “Loop Playback” (same thing I described that’s on the Transport Bar), “Set Selection to View”, “Set Selection to Project”, and Select Loop Region”.
You can either play around with these things yourself to see what they do or you can look it up using the Vegas Online Help, provided with Vegas. The Online Help describes everything I have just described (in a clearer manner too!).
I hope this helps,
Michael M.