If you do not have the problem with other browsers installed on the same machine, then you know it is a Chrome setting of some kind, one that might travel with you whenever you login to a freshly installed version of Chrome. You may have a Chrome extension installed that is buggy or conflicting with another Chrome extension or feature.
If you do have the problem with other browsers installed on the same machine, I would look at either the keyboard settings for a very short repeat setting (even if you don't have this problem with other keys), or an accessibility (disability) setting that forces keys to behave differently than they otherwise might.