There are a couple of ways I could see this being risky:
Start time - If the potential new company doesn't believe you are currently working, then you may need to come up with an explanation for not starting tomorrow which a potential employer may expect. I'd stress the may as most companies may take some time to set up some things for a new employee so this may not be a big deal, but this may be an issue to consider if you have to ask for more time to properly exit from your current role.
Rumor/gossip - There may be the potential for someone at a perspective new company to know where you are that may think this is worth discussing in an interview or after you start in a new role. "Hey, weren't you working at XYZ last week?" or something like that may be asked. I'll admit this isn't necessarily likely but it is a possible risk.
On the bright side, only 2 weeks is an extremely short period of time and thus may not be seen as bad as if you had been working there for many months. At least this would be based from what I've seen in Canada and the U.S. that may or may not be common in other parts of the world.
Freelancing at your old company reduces one a little as this may give you some wiggle room if the company says, "we want you to start tomorrow at 9 am," then you can return with, "my old company's current needs will take some time to resolve. Could I start in a week or two?" which may be fine.
The second risk isn't reduced at all if someone knows you are working at another company. To give an example in the second case, imagine a Jim that worked at Microsoft, currently works at Amazon.com and is applying at Starbucks. Unfortunately for Jim, the people at Starbucks that would be his manager are friends with the people at Amazon.com that are Jim's current co-workers that over a coffee it slips and now Jim could be in trouble in terms of getting the job at Starbucks as they find out something that makes them question if Jim would be honest about his situation. Granted these are large companies that may not have the connections I'm implying, it is just a possible situation that could occur.