If money is not flowing all you are doing by slashing your advertising and marketing budget is breaking the faucet. If your message is out there rain or shine then you can make money rain or shine. But what do you do when revenues fall and you can't afford what you were spending on marketing and advertising anymore? The answer to that is simple. Do more with less.
Find an advertising agency that is willing to work with you on their hourly rate for creative. Ask them to get more creative/aggressive with your ad placement to mitigate costs (a lot of media outlets these days are hurting just like you are and will get your ad out there for a lot less than you might expect), and focus your messages on a specific call to action rather than brand awareness.
Think about it, you know it to be true. When you see ads on TV these days you see restaurants with specific low cost menu items mentioned, car commercials that don't just tell you the car exists and how much it is, but have specific time frames to to get the car at slashed prices. This works in B2B as well. Let your client base know you understand they are hurting and that you are willing to work with them. Get an e-mail blast out there, make some press releases, etc...
In the end you will have more incoming revenue and reduced marketing costs in the lean times than your competition that panicked and shut down all spending.
You can thank me later.