[Lazarus] UniqueInstance issue

[Giuliano Colla]

In an application I'm currently developing, meant to run under RHEL5, I
needed to ensure that no multiple instances were running, so I installed
the UniqueInstance component:
http://sourceforge.net/projects/lazarus-ccr/files/Unique%20Instance/Unique%20Instance%200.2/

Under RHEL5, the only usable combination is:
Lazarus 9.26.2
FPC 2.2.2
i386-linux-gtk2

In this environment, using the TUniqueInstance component leads to this
situation: the first instance runs properly, the second terminates with
an EAccess error in Form Create, which isn't very nice.
If the Component is not enabled at design time, even the first instance
aborts the same way.
Is that something to be expected because of version too new/too old,
wrong fpc version, gtk2 vs gtk, etc.?

I'd like to understand if the matter is worth further investigation or
it's simpler to give up.

BTW UniqueInstanceRaw works perfectly, but I'd prefer a visual component
on the design form, to make life easier to maintainers, provided this
can be achieved with a reasonable effort.

Could someone point me in the right direction?

Thanks,

Giuliano