I am running 5.1 Build 19 Pro.

Every so often two empty groups pop up.
I delete them but they keep coming back.
There is no option to hide empty groups.
How can I get rid of these permanently?

Searching the forums is usually the best way to go, many things have been answered in the past including this.

I could be wrong about this, as I usually have my contact list showing all groups at all times, but I seem to remember groups showing up while still appearing empty if by chance you group by group and have one of those contacts moved into a metacontact. Don't quote me on that, I haven't verified but I do remember having something similar happen a while back.

As for hiding empty groups, there is an option to hide empty groups. It unfortunately was removed from the preferences.

You can set it to hide empty groups by changing the setting within buddies.ini

Supress Empty Buddy Entries=0

The file will be located within your user data folder, vista/7 path should be C:\Users\<username>\AppData\Roaming\Trillian\users \<astra id> unless you have manually specified a different path.

Thanks.

I did search but could find nothing about deleted groups reappearing.
Perhaps my search argument(s) were too restrictive.
The groups in question are Google and Jabber and I have in fact moved contacts from
them to metacontacts in other groups like Friends and Family.

Currently in buddies.ini I have
Supress Empty Buddy Entries=1

which I assume switches on the supression?

Correct, 1 would supress the groups. So you have it set to do that already, but you are experiencing the same issue I had but that was a year or two ago. I'd have to play with it some more to see if/how i resolved it, if I did at all.

Your contact list, do you have it set to Group by Group, or Group by Service?

I have not selected "Group by Service" so I assume Group by Group would be in force.

The empty groups disappeared for a while.
However I just re-installed Windows and the damned things re-appeared despite there being no change in my Trillian settings and with Supress Empty Buddy Entries=1
It seems these entries have a will of their own.