It's been a while since I last used P4Merge, but last time I checked, there was no such strange issue.
I'm trying to open a file in order to compare it (or merge it) with another file. If I start p4merge.exe, and type a directory like
"C:\temp\thisFileHere.txt" in any of the boxes (1st or 2nd), it will load it correctly, as expected.
However, if the path contains latin characteres, such as
"C:\temp\ChampsDeElisée.txt", it simply won't open.
Is there a known issue for this?
I'm currently using 2015.1/1233444.
Short answer: Yes, there is an unreported issue.
Downgraded to 2014.1 and it works as expected.