Here's a simple string response problem that determines if students know that it's the number of protons that determines an atom's identity.  The way I worded the question calls for them to type in "protons", but I didn't want to frustrate students who just typed in "proton".

I needed an adaptive hint. 

• If a student just plain old got the question wrong, they got the default hint. (see green bracket below)
• If they typed in "proton", then they got the hint that tells them to enter it again, but make their answer plural. (blue bracket)

I visited the faq-o-matic loncapa thing, and used their template to make this problem.  Just in case someone out there is having my same problem, I decided to post how I got the problem working.  The whole problem [for me] was setting the "stringhint" (red below).  You have to put in the close-but-wrong answer proton and make up a name for the hint plural, and then once you're in the "hintpart" area (blue  below), you must refer to your stringhint by name.

For me it was MUCH easier to use the EditXML option here, because all of the blocks in the Edit tool messed me up for like half an hour.