Voltage level too low for MAX232
I'm assuming you're using TI's MAX232. Other than missing the bypass capacitor, your schematic seems fine. See below the Typical Operating Circuit from the datasheet for a comparison.



Also, regarding Jim's comments, according to the datasheet, your C4 capacitor negative (short) lead (which corresponds to C3 in the circuit below) can be connected to either VCC or GND (see footnote).

So, I'm guessing that either -


your IC has failed
your connections are different from the schematics you presented


A good quality picture of your board or breadboard would help us determine if the problem is in your circuit or not.

Also, if you have access to an oscilloscope, you should see a nice square wave on the kHz range at the capacitors leads (not sure which ones, but C1 and C2 certainly). That would mean the IC's charge pumps are working fine. I'll post a shot when I get home so you can see what it looks like. From memory, I would say that they are about 1V in amplitude.

In any case, I would add the bypass capacitor as well, just to make sure the MAX232 power supply is stable. Adding the correct bypass capacitor made a difference for me once.