Another Mozillla Thunderbird question

[#1]

If I have opened Mozilla Thunderbird, even if I have minimised it, and then I try to use another program, my pc runs very slowly. If I then shut Thunderbird, even though the slow running program is still running, the slow running program then goes at normal speed.
For example, I copied and pasted part of an e-mail to Word, minimised Thunderbird, then tried to print the copy from Word (I didn't want to print the whole e-mail, and I would have preferred not to have to come out of Thunderbird). The print did nothing apart from the window it uses to tell you how much ink you have, so after waiting ages, I shut down Thunderbird, and the printer started immediately.
Is this normal for Thunderbird, or is there something I can do so that Thunderbird doesn't 'block' my pc? It seems a bit of a nuisance to have to shut it down, if I will want to reopen it immediately after doing, in this case, a print.
This isn't the only program Thunderbird seems to obstruct
Thanks

[#2]

Thunderbird works fine for me , no slow down at all , win 7  x64 
no idea why it slows yours 

[#3]

Thunderbird works fine for me too - if it is Thunderbird that I am actually using. However, if I have Thunderbird open, but am not using it because I temporarily moved on to running some other program, that other program runs very slowly. I shut down Thunderbird and the other program works at normal speed. It is that, that I do not understand

[#4]

If you untick "Enable Global Search and Indexer", assuming it is already ticked, that might help.  It may be doing some indexing behind the scenes.  Just a guess!
See attached pdf.

[#5]

Thanks pnf. Have tried your suggestion but it doesn't seem to have done the trick. Never mind - was worth suggesting

[#6]

To identify if the problem is an add-on, or just to eliminate them from enquiries, you may get a clue if you try running Thunderbird in its Safe Mode.
In Thunderbird select:  Help -> "Restart with Add-ons Disabled..."
If Thunderbird now doesn't affect the other programs then you could try and work out which add-on is the cause by disabling/re-enabling them one at a time.

[#7]

Just out of interest do you have Thunderbird and Firefox 13 or below running at the same time?
As when TB was in it's beta stage I found that TB would open FF in the background thus using twice resources.

[#8]

Sorry for delay - have been away. The running in safe mode seems to have done the trick.
Thanks to all