$form['#attributes']['enctype'] unneeded in some cases?

I had the same error, and crafted a potential solution. Using the devel module, I traced the error that I got as follows:
* warning: preg_match() expects parameter 2 to be string, array given in /includes/bootstrap.inc on line 670.
* preg_match
* file/line: /includes/bootstrap.inc: 670
* arguments: /^./us,

Array
(
    [0] => multipart/form-data
    [1] => multipart/form-data
)

That second argument is an array, and as the error we're getting so handily notified us, it should be a string. Tracing back further, I found:
* drupal_attributes
* file/line: /includes/form.inc: 1433
* arguments:

Array
(
    [enctype] => Array
        (
            [0] => multipart/form-data
            [1] => multipart/form-data
        )

)

The desired string ("multipart/form-data") is somehow being written in twice. I don't have the time to figure out how or why, but in the hopes that it would fix it, I commented out the line $form['#attributes']['enctype'] = 'multipart/form-data'; in reg_with_pic.module...

And that fixed it!

This clearly may not be a universal solution. But it worked for me, so hopefully that will help.

I can back that up-- I am running nodeprofile too. Looks like instead of commenting that out, maybe it could check to see if nodeprofile is activated and then act accordingly.