Quanta suddenly stopped accenting vowels

Dear folks,

I don't know if this topic has already been addressed. I have googled a 
lot before deciding to post here, so please be patient with me.

I'm Ubuntu 8.04 (hardy) 64 bits and Quanta 3.5.9 user.

My native language uses many vowels with accents (like á, õ, etc.). In 
Font Editor mode Quanta used to accentuate them normally, but this 
morning it started refusing to do so for some odd reason.

For example, to make "á" I type ' then a. But now it is separating the 
characters instead of giving me an accented vowel as it did before.

I haven't changed anything on the settings nor I could be able to find 
any setting related to the problem.

And, as you can see, other applications haven't been affected, so it's 
not a system setting issue.

Would anyone be so kind as to give me a hand on this please?

Thanks in advance,

Marcelo