In the world of sales there are differing opinions about the answer to this question. Some feel that when a prospect/client asks you a question, you should always answer them. Others say that a question should always be answered with another question. Still others claim that whenever a client mentions a problem, you should ask at least three questions to get to the root of that problem.
So, what's the answer? Well, a combination of all the above, depending on the circumstance, and, most importantly, the client or prospect's mood. We need to be aware and mindful of the cues we receive to let us know what kind of day our clients are having. Cues like tone of voice, body language, even words they are using.
When the client is in an upbeat, or almost playful mood you can answer a question with another question. If a client asks "So, what are you trying to sell me today?" you can chuckle and answer "What are you buying today?"
Conversely, an upset client will not tolerate unanswered questions. In that situation, answer their question, then follow up with a statement acknowledging their feelings and ask another question. This might sound like "You're correct, we made a mistake, your complete order will not be delivered Friday as we thought, but next Monday instead. I understand that puts you in a tough spot. I'd be upset as well. What might we do to make this right for you?"
This approach allows you to accept responsibility (you should), makes the client realize that you understand and empathize with their predicament (strengthens your credibility because you're focused on their needs) and puts them back in control of the conversation (this is always your goal - for the client to be engaged and in the driver's seat).
Notice that there was no mention as to why the mistake took place, which department/individual was responsible, etc. Since that information is really of no importance to the client don't bother sharing it. You'll only sound like you're making excuses or blaming someone else, both of which make you look ridiculous and lead to distrust.
The art of knowing when to ask and when to answer is one that is perfected over time, with trial and error and numerous attempts. Remember one important rule-of-thumb. Just as with your significant other, don't make your clients ask the same question repeatedly without giving an answer - it's best to give an answer the second time the same question is asked.