Personally, I'd either let the 5' step be able to take place so long as the persons half movement is still greater than 5' (ie 10'+) or, less likely, I would allow them to make a partial charge over the 5' (after all, to them it feels like 10'
).
One or the other, but definately not neither.. well, maybe both, that could be fun too. I like having very strange reasons to cast normally harmful spells on the party (such as ray of enfeeblement).

One or the other, but definately not neither.. well, maybe both, that could be fun too. I like having very strange reasons to cast normally harmful spells on the party (such as ray of enfeeblement).