I am having TextArea inside the custom type editor as shown below. But amazinlgy textarea border is invisible. It seems that editor “text” style is not accepting textarea as inner thing in div.
Style “.dhx_cal_ltext textarea” will be applied to all textareas inside the lightbox, including the one in your custom form block. So if you have some visual problems with textarea in the custom form block - still try to alter styles of above mentioned css rule.