"linearGradient" errors

[Guest]

I'm systematically updating the PCs in my office from Kubuntu 12.04 to 16.04 (via 14.04 of course).

On one of these, when the users runs an application like kwrite or kate it starts fine, but as soon as she types in the application, dozens of errors of the form:

Could not resolve property : linearGradient4548
Could not resolve property : linearGradient4532
Could not resolve property : linearGradient4582
Could not resolve property : linearGradient4566
Could not resolve property : linearGradient4548

appear on the command line.

Googling has turned up nothing - can anyone tell me what these errors are and how I can get rid of them?

Initially after this error there was some kind of graphics glitch as the klauncher menu didn't open, and indeed right-clicks on the desktop did nothing. Reinstalling the nvidia driver and asking the user to delete her .kde and .config directories seems to have cleared that issue, but not the lineargradient errors.

[Guest]

Same issue for me as for @PhilEvans - dolphin chokes with the following error:

Could not resolve property : linearGradient4538
Could not resolve property : linearGradient4588
Could not resolve property : linearGradient4554
Could not resolve property : linearGradient4572
Could not resolve property : linearGradient4532
Could not resolve property : linearGradient4582
...

I am running Kubuntu 16.04 and using the basic VESA video driver.

lshw reports:
*-display UNCLAIMED
description: VGA compatible controller
product: Broadwell-U Integrated Graphics
vendor: Intel Corporation
physical id: 2
bus info: pci@0000:00:02.0
version: 09
width: 64 bits
clock: 33MHz
capabilities: msi pm vga_controller bus_master cap_list
configuration: latency=0
resources: memory:e0000000-e0ffffff memory:d0000000-dfffffff ioport:3000(size=64)

Please let me know if there is other information that would help resolve this.