SMF 2.0 RC5 Server hangs up when registering new user

[bbrodnik]

When new user fills up registration form and cliks Register button, it seems like server hangs up. Following message appears in browser:

The website cannot display the page    HTTP 500
Most likely causes:
  •The website is under maintenance.
  •The website has a programming error.
What you can try:
  Refresh the page.
  Go back to the previous page.
More information
  This error (HTTP 500 Internal Server Error) means that the website you are visiting had a server problem which prevented the webpage from displaying.
  For more information about HTTP errors, see Help.

The same appears in admin mode in
  Forum MuLeMa » Administration Center » Members » View All Members > Awaiting Activation (1)
when try to perfom "Remind and send email".

Sending email from member profiles works with no problems.

It only works fine if Registration settings are ajusted to "Immediate registration" and "Send welcome email to new members" is unchecked. If any messaging option to newly registration user is involved, registration hangs.

[kat]