Blame Windows for changing the drive letters. You have configured a profile to point at a letter that now isn't there (or worse, is now pointing to a different device, that might be highly inappropriate...). This is a bit like saying that when you add a telephone number to a Contact on your phone, if that person's phone number then changes, the Contact should 'know' this and self-adjust (what to?), which isn't going to happen.
This should help. Note that in the commercial versions, you can refer to drives by volume name (which won't change unless you change them) or serial (which won't change unless you re-format the drive). There's a link in that KB article with more details, but this isn't supported in the free version.
This should help. Note that in the commercial versions, you can refer to drives by volume name (which won't change unless you change them) or serial (which won't change unless you re-format the drive). There's a link in that KB article with more details, but this isn't supported in the free version.