You have received 40 or so views in less than an hour. Sometimes it takes days for other suers to drop by and your post is arriving during the start of a long holiday weekend in the Sates so it might not be till next week befor someone who really knows how to answer this shows up. Your post is being viewed by people who want to know if you are serious but have no help to offer. Woudl you rather they posted nonsense? I have never had AE jumpt back to the start of the timeline and posting that information does not help you. I can assume you have a some sort of pref incorrectly set or your keyboard has been tweaked at the OS level to interpret a spacebar in AE as a Media Start command.

From the AE help system:

To modify keyboard shortcuts, use the KeyEd Up script from Jeff Almasol, which is available on the Adobe After Effects Exchange website.

Sebastien Perier provides instructions on his website for assigning keyboard shortcuts to scripts so that you can run a script with a single keystroke. This technique relies on the KeyEd Up script.

For information on remapping keyboard shortcuts for keyboard layouts other than the standard US English layout, see Jonas Hummelstrand’s website.

For a reference of keyboard shortcuts, see Keyboard shortcuts reference.

Note: On Mac OS, some keyboard commands for interacting with the operating system conflict with keyboard commands for interacting with After Effects. Select Use System Shortcut Keys in the General preferences to override the After Effects keyboard command in some cases in which there’s a conflict with the Mac OS keyboard command.

Time navigation (keyboard shortcuts)

#

Here is you original post:

>Right now the cursor always goes to the start of the timeline after i press the spacebar.<

And here is your present situation, implying some kind of dissatisfaction with Adobe and with me, the only peorson in 50 views to offer anything:

> Not sure why copying and pasting the help file can help anyone.<

That is because most people, apparently not including you and you are now the exception, post questions like your without bothering to do any research at all.

I just opened a project in AE. Pusing and starting the timeline with the spacebar works exactly has it has always performed. There are a few ways to make it go back to the start but it requires more than the spacebar to return to the start of the timeline. If your machine does this, it is unusual.

This claim of yours:

> Every installation of AE I've ever used on a Mac or PC for five years has done this and until recently I've been fortunate to use Flame, Inferno or Combustion for my compositing. It's not a configuration problem unless it's a standard setup that every experienced AE user changes the moment they sit in front of a fresh install. <

is in direct contradiction to every installation of After Effects I have ever used. While it is difficult to believe this claim of yours, I have no reason to disbelieve you. But there is no intrinsic behavior in AE's keyboard shortcuts that would cause the spacebar to take the cursor all the way back to the beginning of a comp unless you deliberately tell it do so.

Your additional information:

> It's time for me to learn my way around AE's strange behaviour. But the first and most pressing order of the day is to solve this 'timeline cursor jumping to the beginning of the timeline when I press the space bar or zero key' problem.<

This use of 0 is not described in your original post. You did not inform us you had done all that other research. You just made a statement. In fact, your OP does not even include a question, it's just a statement. What was anyone to do with that? And your second post, in addition to complaining about the level of support you received includes this question: >  is this possible to do in AE?< How are we to interpret THAT?

Do you know how to use the Preview window controls? That is the only place I know of that includes a looping option.