The bad news is, this is a known issue. The good news is that there is a simple workaround and we should have it fixed by the end of this year.
The problem is that the system cannot handle special characters in the first name, last name or alias fields of the NI User Profile.
To modify these fields of your NI User Profile, visit www.ni.com/profile.
Once there are no special characters in these fields, you will have no problem logging in. If you do have other problems logging in, please send an email to webmaster@ni.com and we will work to resolve it.
Thanks!
Molly K
National Instruments
Web Support & Operations