They just freeze your accounts without warning!

I keep my short-term savings in my flexi home loan, transferring funds out when and as needed. As a rule I leave very little money in my cheque account. Today I can't transfer any funds. After chatting with a banking consultant, I'm informed there is a "Know-your-client" hold on my home loan account. How does that happen without any warning or reason given? Now I have to complete a form and send my ID and proof-of-address again. Why? If it is just routine, why not inform me in advance? Luckily I found out now, because if it was the end of the month when debit orders go off and I couldn't transfer any money, my cheque account would be overdraft!