... and forgot to say. Reinstalled 5.2a ([font=courier new]Sweet Home 3D ® Version 5.2a Java version 1.8.0_74 / 32 bit / 0.6 GB max[/font]), and SH3D worked beautifully.

ok

PS - Rather a worrying experience, starting the beta really made everything act up. And the WIFI issues continued after reinstalling 5.2.a (connections kept being killed) until reboot - but that may be a coincidence/network interference of sorts.