problem experiences with latest update on 1.0.0rc3.
Severity should be MAJOR.
Soultion included in Additional information.

"$p_type == 2048" is contrary to Mantis coding standards. It should have been written "2048 == $p_type" which would have also caught the error before it was committed.

Fixing in trunk a.k.a. 1.1.0

core/error_api.php -> 1.49

Will someone please merge that to the 1.0.0 branch...

I had a look at 1.0.0rc3 and this ($p_type = 2048) check doesn't exist. Are you sure this issue is applicable to 1.0.0rc3?

Excuse me fo not clear description: "latest update on" means the file was updated after rc3.
The described issue appeared after 1.0.0rc3, was found at CVS as Branch:MAIN

http://cvs.sourceforge.net/viewcvs.py/mantisbt/mantisbt/core/error_api.php?rev=1.48&sortby=date&view=markup

line was:
if ( 0 == error_reporting() || $p_type = 2048) {

Now it is Branch:MAIN:

http://cvs.sourceforge.net/viewcvs.py/mantisbt/mantisbt/core/error_api.php?rev=1.48&sortby=date&view=markup

the line is correct correct already (fix posted by ryandesign):
if ( 0 == error_reporting() || 2048 == $p_type ) {

The issue looks to be fixed. Works correctly with my code.

Sorry, I had just looked at HEAD. So does anything need to be done to any tags / branches to make sure the problem doesn't make its way into 1.0.0rc4 or is this issue resolved? (Sorry, I still need to read that CVS tag / branching manual.)

I do not know the procedure of releaseing for this project exactly, but I guess it looks like nothing more have to be changed, if for generating version 1.0.0rc4, Branch=MAIN and CVS Tag=HEAD will be used. The issue already fixed in mentioned branch\tag, and no more available branches/tags for this priject in CVS after 1.0.0rc3.
So, current issue state can be turned to RESOLVED (FIXED)