I often find it necessary to flush all clipboard data. This simple .jsee macro (unlike using external utilities) turns the Paste icon in the EmEditor basic toolbar inactive (uncolored).
var check = checkClip();
while (check != 0) {
clipboardData.clearData();
var check = checkClip();
}
Quit();
function checkClip(str1, str2, str3, len1, len2, len3) {
str1 = clipboardData.getData("Text");
len1 = str1.length;
str2 = clipboardData.getData("BoxText");
len2 = str2.length;
str3 = clipboardData.getData("html", 0);
len3 = str3.length;
return len1 + len2 + len3
}