If I have a Houdini 6 file and open it in Houdini 6.1 save it and then open it again in 6.0 will I encounter any serious problems. I ask this because I need to be able to work on a project on a machine with 6.0 and another machine with 6.1.

Thanks

Unfortunately there's no simple answer to the question. It depends on what you had in the file. You can be assured it will cause at least *some* grief, if not catastrophic. Avoid.
You may be lucky, but it's luck. I don't like trusting to luck.
Note there are a couple of envars you can set to try to minimize problems:

HOUDINI6_COMPATIBILITY
HOUDINI6_FILTER_COMPATIBILITY

If you set these when running 6.1 they *might* get you through some problems.

Still. Avoid.

Cheers,

J.C.