it installs a new netapi32.dll which badly fragments the virtual address space of a 32 Bit process preventing 2 GB applications (java.exe is one of them) to allocate more than 850 MB contigious memory.
3 GB enabled 32 bit applications may also be affected by this.
64 bit applications are not affected.
32 bit applications on 64 bit operating systems are affected.
there are two solutions :
1. uninstall KB921883
2. install KB924054