Reference to undefined property E.cache[a][d]

I am new at this so please be patient. I will try to be as detailed as I can.

I have just completed an install of D6.2 on sitegrounds server (MySQL database 5.0.45 //
PHP 5.2.5 // 1.3.37 [Unix]) using fantistico.

I then proceeded to Administer >> Site building
>> Modules to enable some modules. Firebug - I'm using Firefox 3 - alerted me to the following 2 errors:

reference to undefined property E.cache[a][d]
[Break on this error] eval(function(p,a,c,k,e,r){e=function(c)...h|borderTopWidth|abbr'.split('|'),0,{}))
jquery.js?K (line 13)

variable args redeclares argument
[Break on this error] var args = args || {};\n
drupal.js?K (line 139)

Site Building >> Blocks returns the same errors along with the following further errors:

anonymous function does not always return a value
[Break on this error] };\n
tabledrag.js?K (line 155)
anonymous function does not always return a value
[Break on this error] });\n
tabledrag.js?K (line 349)
anonymous function does not always return a value
[Break on this error] });\n
tabledrag.js?K (line 362)
anonymous function does not always return a value
[Break on this error] };\n
tabledrag.js?K (line 751)

More errors display at other pages, but it they are similar to the ones above. I could go through and make a list of all the different errors if needed. Perhaps the ones above provide a start?

Like I said above, being new at building websites I don't know what these errors mean except that I would have hoped that a clean install of D6 would not produce these results. Do I just go ahead and start building the site regardless of the errors - like I said there does not appear to be any visible issues with the install?