U.S. - CERT Current Activity Warnings:

Microsoft has released an update to address a vulnerability in
Microsoft Office as part of the Microsoft Security Bulletin Summary
for May 2009. By convincing a user to open a specially crafted
PowerPoint file, an attacker may be able to execute arbitrary code.
See:
<http://www.microsoft.com/technet/security/Bulletin/MS09-may.mspx>

We all use Adobe Reader or Acrobat so read the following:
Adobe has released security updates to address a vulnerability that
affects Reader 9.1 and earlier and Acrobat 9.1 and earlier. This
vulnerability could allow an attacker to execute arbitrary code or
cause a denial-of-service condition.
<http://www.adobe.com/support/security/bulletins/apsb09-06.html>

Apple and Safari (Browser) Users:
Apple has released Security Update 2009-002 and Mac OS X v10.5.7 to
address multiple vulnerabilities in a number of applications. These
vulnerabilities may allow an attacker to execute arbitrary code,
obtain sensitive information, cause a denial-of-service condition,
leverage additional attacks, or obtain elevated privileges.

Additionally, Apple has released Safari 3.2.3 to address
vulnerabilities in libxml, Safari, and Webkit. These vulnerabilities
may allow an attacker to execute arbitrary code or cause a
denial-of-service condition.
<http://support.apple.com/kb/HT3549>

<http://support.apple.com/kb/HT3550>

Notice on the above:
Safari is constantly upgrading and testing the browser. Currently 4.0 is a Beta product. For safety reasons use:
Firefox (the current version) or if you use Windows: Microsoft's browser.
Always check for updates. Download automatic update software from Microsoft, Apple, or Adobe. Mozilla (Firefox) update device is built in.

What version of Office, 2003 or 2007?

Macs can be hacked too . It's not just a Windows problem.

Tell me about it. When I had AOL on my Mac everything in the machine was destroyed. When I got a G4 machine, and now two Intel Macs, I use two firewall, an Apple router with a built in fire wall, and run Virus Checkers.
Updates: daily. Apple keeps coming out with new firmware daily.
Windows on Mac took 35 minutes to update security. I run all kinds of security software on Parallels (The Windows Vista and XP on my Mac). XP has my chess programs and games.

Thanks!