Above the preview window is an icon that looks like a rectangle with a split circle inside it. Pull down the menu for it by clicking the triangle to the right of it. Choose Select All. This bypasses all video effects.
If your events are all on one track, just right-click the FX button and select Bypass All. then after the render, right-click again and select Enable All. If not, just do this for each track you want to disable the FX's for.
I note that Vegas 8 scripting enhancements include this line:
* The new Bypass property of Effect objects allow you to get or set
Thus, one of the scripting gurus could add the ability to store the collection of all fX objects, and remember which ones are enabled or disabled. Then, the script could disable them ALL. Later, it would let you re-enable all of those that were enabled at the time you disabled them all.
The script could simply disable and then re-enable all fX, but this would likely cause problems because sometimes users WANT to leave some fX disabled.