Possible Cloaking Penalty

Need help to determine if my site is getting a cloaking penalty from Google

[oubc67]

Over the past 2 weeks I have been seeing some of the same things happening with my site with regards to Google. We used to have 700 pages indexed - now we have 140. We also no longer even show up for our own company name or any other keywords that we used to rank in the top 10 for.

After looking over the site again, I noticed that we have had a browser.js file which determines which type of web browser is being used and then tweaks the site a bit (calls a different style sheet) based on the type of browser. The main purpose of this is to make sure our site is displayed properly across all major browsers. I am wondering if this javascript file is now causing problems (with the rumor that Google now reads javascript). Here is the code:

function Is() {
agent = navigator.userAgent.toLowerCase();
this.major = parseInt(navigator.appVersion);
this.minor = parseFloat(navigator.appVersion);
this.ns = ((agent.indexOf('mozilla')!= -1) && ((agent.indexOf('spoofer') == -1) && (agent.indexOf('compatible') == -1)));
this.ns4 = (this.ns && (this.major == 4));
this.ns6 = (this.ns && (this.major >= 5));
this.ie = (agent.indexOf("msie")!= -1);
this.ie3 = (this.ie && (this.major < 4));
this.ie4 = (this.ie && (this.major == 4) && (agent.indexOf("msie 5.0") == -1));
this.ie5 = (this.ie && (this.major == 4) && (agent.indexOf("msie 5.0")!= -1));
this.ie55 = (this.ie && (this.major == 4) && (agent.indexOf("msie 5.5")!= -1));
this.ie6 = (this.ie && (agent.indexOf("msie 6.0")!=-1) );
}

var is = new Is();

if (is.ns4) //for netscape4 and Firefox
document.write('<link rel="stylesheet" type="text/css" href="style_nav.css" title="master">');

if (is.ns6)// for netscape 6

document.write('<link rel="stylesheet" type="text/css" href="style_gecko.css" title="master">');

if (is.ie4¦¦is.ie5¦¦is.ie55¦¦is.ie6) //for IE

document.write('<link rel="stylesheet" type="text/css" href="style_ie.css" title="master">');

Can someone please tell me if they think this would cause a Google cloaking penalty? This code has been live on the site for 2 years and up until now we have had great rankings.

Thanks!