這句有錯嗎?

We have lost contact after she had moved to Tuen Mun.
這句中的"have lost" 沒有用錯。反是 "had moved" 不及 "moved" 好。

"have lost" 是 present perfect tense。 Present perfect tense 其中的一個用法是用來表達一個事實發生在以前的一個時間點，而這事實至到現在都维持不變。

"We have lost contact after she moved to Tuen Mun" 的意思是：
1) We lost contact after she moved to Tuen Mun
2) We did not have contact again
3) We still do not have contact now.

"have lost" 吻合 present perfect tense 的三個條件，所以在這句子裹是用得正確的。

We have lost contact after she had moved to Tuen Mun.

Without any doubt, It's correct. But it's better write, particularly verbally, we
should say it like this:

We've lost contact since she moved to Tuen-Mun.

"since" is a better conjunction to use here.

After she had moved to Tuen Mun,we have lost her contect

change the possesion

I don't not agree with Jenkin on his point
" had moved是必要的tense form來表示搬去屯門這動作是在(失去聯絡)以前已經發生的，而不是一件獨立過去發生的事件。"

after 已清楚表示搬去屯門發生在失去聯絡之前，past perfect tense 並非必要。

2010-08-13 06:08:04 補充：
The sentence looks (reads) better if "after" is replaced with "since"

We have lost contact since she moved to Tuen Mun.
We have not been in contact since she moved to Tuen Mun. (Wongtak Yee's version)

2010-08-13 06:16:09 補充：
Past perfect tense is necessary in situations where we are talking about two past events and the writer wants to tell the sequential order. For the case in question, the main clause (lost contact) is not a past event as Jenkin pointed out "失去聯絡會是「直到現在」".

2010-08-13 06:19:16 補充：
搬去屯門 happened in the past and the events justify the use of simple past tense in the adverb clause.

Rewrite:

Either (1) We have lost contact after she moved to Tuen Mun.
Or (2) We lost contact after she had moved to Tuen Mun.

I am in favour of (2).

Reasons:

Simple past tense is used when we put emphasis on the time of action.
Present Perfect tense is used when we put emphasis on the action, regardless of the time.

Now please judge if you want to focus on (i) the time you lost contact with her or (ii) the fact that you have lost contact with her.

It seems to me that the focus is on the time, as can be seen from 'after she moved to Tuen Mun'.

Example:

The goods were delivered last Monday. (emphasis on the date of delivery)
The goods have been delivered. (emphasis on the fact of delivery done)

這句有兩個tense的子句。第一個你問到的have lost (present perfect)，另一個是had moved (past perfect)。兩個子句之間的連接詞是after。

要明白tense是否用啱便要看你識唔識after這個連接詞前後事件的關係了。

有些人after直覺以為x after y便錯誤地以為x的時間在y後，但英文的after不等同中文的「之後」的前後編排，這句搬了去屯門然後才失去聯絡，因此相對而言move去屯門的時間性會是「過去」，而失去聯絡會是「直到現在」，這樣可以了解為何用have lost(現在的完成式)和had moved(過去的完成式)。

接著有人會話點解唔用moved(simple past)表示已過去(搬了)便可以，為何要用複雜的past perfect。這個便要回到你是否學懂after前後文的relative caluse相對子句所要說出的相對時間關係。had moved是必要的tense form來表示搬去屯門這動作是在(失去聯絡)以前已經發生的，而不是一件獨立過去發生的事件。

接著回到你的問題，那麼為何after前的子句要用present perfect而唔係用simple past tense (lost)，這是因為當說這話時，雖然意識上一定有一段時間聯絡不到了，看似是「已經」發生了的情況，但是在表達上你是「現在」說出這已經出現的情況，所以會用present(代表你所處的時空)加上past participle(代表事情已經發生)，這是perect tense的實際意思，這規則在不是after相對的情況下也是如此。例如：I have done my homework just before the deadline.明顯地你已經做完了功課並且截止前交了，但由於你是正在講述關於你做和交功課的過程(過程本身已是過去)，但是主角是你的描述，所以語法上會講成present perfect(現在-完成)。小學的英文會解釋這tense是剛完成才會用，過去了就不會這樣寫，但真正英文是可以任何時間你在說已經發生的事都可以用的，只是要小心句子是想說你或那事的評述(用perfect tense)，還是記敘已發生的事(用past tense)

以上兩個因素加埋這句用了present perfect - after - past perfect是要表達兩個情況相對你現在講出來時的時間和情況的關係。所以沒有錯。給你知道他們自從她搬了去屯門之後到目前仍然未有聯絡上她 (present perfect - after - past perfect) 。並不是表示他們在她搬了去屯門之後便失去聯絡 (past - after - past perfect)。或記述在她搬了去屯門之後他們便從此失去聯絡了 (past - after - past)。三種tenses的組句文法上都以是沒錯的，但意思卻有點分別吧。

We lost the contact after she had moved to Tuen Mun!

2010-08-12 14:49:42 補充：
I think this sentence is wrong

2010-08-12 16:24:09 補充：
我做補充時,discovered something...........
本書就話,兩樣都做左(PAST),有連接詞(AFTER,BEFORE.......)邊樣做先就用had moved.之後就用past tense(lost)