No! If done properly, switching hosting companies or IP address will NOT affect your Google ranking. Done properly means that there is no down time during the transition. If there is some down time then you could experience a temporary drop if the Googlebot just happened to come at that time. And, according the Murphy, it will. However, follow these steps suggested by Google and your transition should come off without a hitch: <--break->

1. Bring a copy of your site up at the new IP address.
2. Update your nameserver to point to the new IP address.