Is there any way that this could lead to legal trouble? If you're taking a week of vacation from your current job, that seems to imply that you're now drawing two salaries simultaneously; double dipping, so to speak. Sure, your current job isn't expecting you to be working, but they are expecting you to be getting rest and relaxation, and be able to come back fresher, not, say, come back stressed out after not quite cutting it for a week at another company.
Your job has no business "expecting" anything about what you do on your vacation. It's your time, do whatever you want.
For an example, see a poster above who goes on military training at that time, - it likely is more exhausting than any computer job, but perfectly okay anyways.
Except where most larger companies do require you to declare outside work or advisory/consulting arrangements, and would hold you in breach of employment terms if you did not.
