Yeah.
I been getting these "errors" on many MG casinos.
Also when my pc (Wind7,64bit) was new.
I play on many MG casinos,and i get the script error on,lets say,about 30% of them. (and yes,if i get it once i always get them the same place)
I can give you all the names (casino groups) that gives me this error,if that are of any interest.
IE does NOT adhere to agreed standards, and this can sometimes cause such errors. Microsoft seems to think it is in charge of international HTML standards, but it is not.
Microgaming expect IE to be the default browser, yet do NOT use the same bespoke standards as Microsoft, but the international standards (which they are SUPPOSED to be using anyway). This can generate these errors. They WILL keep on happening once they start because they are a property of the website being displayed by the casino lobby using the browser plug-in. They will keep on happening until the casino changes the content of it's default lobby home page, at which point they could disappear just as quickly as they started.
Despite being an irritant, I have not seen any real consequence of such errors, and the casino seems happy if you bypass the error using "continue running scripts" options upon receiving this error.
The most common error I have been getting is an "object" error, usually of the type "this object does not support.........." followed by a line number and brief excerpt of the offending code.
Other than normal maintenance, such as CCleaner as suggested, and keeping up with updates, there is little that can be done by the user except change browser, or switch off the script debugging to prevent the annoying (and usually irrelevant) interruptions.
MGS Viper lobbies don't like IE NOT to be the default browser, and changing browser may produce more problems than it solves.
I hear IE 9 is coming out soon, and Microsoft have "fixed" some issues known with the current IE 8, so trying IE 9 (Beta) might be worth a shot.
Vista and casinos didn't get along too well for over a year, and Windows 7 is still new enough for bugs to still remain with niche applications (such as online casinos).