This is 64-bit Windows 8, version 6.2, build 9200, running on an AMD A8 4500M board in an HP Pavilion G6 notebook PC with 8gb of memory. Mouse, not touchscreen.
Calc version is AOO 341m1, build 9593 Rev 1372282.
I run Calc on .ods files selected from/in their containing folder using the Windows File Explorer file browser.
If I spend too long editing a file, I find that the file browser window becomes inaccessible.  Hovering anywhere over the browser with the mouse pointer changes the cursor to the little blue I-am-busy-please-wait ring, but the browser never becomes available again, and closing it with Task Manager malfunctions in a very old-fashioned way, preventing the screen and objects behind the browser from being visually refreshed and becoming active again.
A further instance of the file browser can be opened but the screen gets soooo messy. The only answer seems to be a re-boot. Now I've not got XP anymore, I don't actually KNOW how else I could re-start my Windows Desktop display.
I have never seen this happen on my (64-bit AMD Sempron processor) 3gb desktop PC that's running OO341 on the 32-bit version of Windows 8.
Do you think it might help if I switch to LibreOffice ? The only thing is, I'm worried that their calculating engine might not be up to the depth of expression bracketing and nesting I'm running - it's definitely too deep for .xls.
I could add a PrintScreen dump, but it really would look just like a regular file browser.